JPH0651336B2 - Raw material extruder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double-screw extruder, and in particular to abrasion during rotation by removing the screw from the barrel wall of the extruder and minimizing the tendency to wear contact with the wall. Bearings for an extruder with a separate feed, in which each parallel screw and barrel are provided near the exit end of the extruder to provide a substantially uniform pressure distribution. The present invention relates to a structure of an extruder and a method of extruding a screw support that provides a function.

Generally, an extruder is an industrial machine that includes an elongated tubular barrel, a feedstock inlet at one end of the barrel, and an orifice die with a decreasing cross-sectional area near the other end. 1 in the barrel
One or more elongate axially rotatable winged extrusion screws are attached and serve to transfer the material along its length. In addition, the entire extruder is usually designed to heat, pressurize and fluidize the feedstock being processed under high shear and temperature conditions. Extruders are used to process various materials such as thermoplastics and crops.
In crop treatment, the extruder is used for cooking and processing the crop. For example, many crops such as soybean, corn and wheat are processed by an extruder.

One type of extruder that is widely used is the single-screw extruder. It has a single elongated extrusion screw within a substantially circular barrel. This type of extruder is commonly used for crop treatment and has been successful for many years. Another type of extruder is the double screw machine. The device has a pair of juxtaposed elongated winged screws in a barrel having a pair of lateral juxtaposed conical cylinders. The screws in such a double screw device are rotating in opposite directions or together in a clockwise direction. Such double-screw extruders have been widely used until now, especially in the plastics industry and the field of crop processing.

The double-screw extruder has the great advantage that it has a more aggressive suction-discharge action compared to the single-screw device. That is, in a single screw extruder, when the raw material advances in the longitudinal direction of the tubular portion, the raw material makes a considerable forward and backward movement, and the drag flow d
evice), which means that it is ineffective, especially when processing highly viscous feedstocks. On the other hand, in the double screw apparatus, the front-back slippage of this raw material during the processing operation is substantially reduced. Therefore, a double screw extruder is generally selected for processing a highly viscous substance such as a synthetic resin.

Despite these advantages, the dual screw extruder has certain operational problems. The biggest problem is the easy wear of mechanical elements. In particular, the pressure generated in the sections where the screws are engaged with each other generates an outwardly directed force that pulls the screws out and causes the screws to come into contact with the adjacent cylinder wall, causing wear. Of. This also wears the screen and barrel,
As a result, maintenance costs and machine downtime are increased. It is well known that the double screw extruder generates a muffled noise when the screw improperly slides against the wall of the cylinder during the work.

Yet another problem is that different rates of feed are provided to the feedstock in the outer sections of the screw compared to the sections in which the screws are interengaging. That is, the raw material screw moving along the extruder near the outer section of the screw will move faster than the raw material moving along the extruder in the interengaging section. This is best seen at the exit of the extruder, where the feed passes through the outer die holes at a higher rate than the feed through the central opening. As can be seen, such speed differences should be prevented as they cause uneven regulation and flow conditions within the extruder. Various attempts have been made in the past to reduce this speed differential problem by providing elongated die spacers between the ends of the screw and the actual extrusion die. This reduced the speed difference, but the use of this die spacer resulted in dead spots and stagnation of the raw material to be processed, as well as burning. This has been a major concern in the extrusion of food or other biological material.

US Pat. No. 410,969 discloses a double screw plastic extruder with a short weight attached to the front ends of both screws. This structure appears to be defective for many reasons. In particular, this smooth weight does not actively transfer the raw material along the longitudinal direction of the weight, and does not provide a substantially uniform raw material distribution and pressure distribution around the weight.

The double screw extruder therefore has obvious drawbacks as well as some major drawbacks which limit its use.

Accordingly, the present invention provides an improved dual screw extruder that alleviates or minimizes many of the above problems. Generally speaking, the extruder of the present invention includes an elongated tubular section having an inwardly extending section generally shown in FIG. 8 having parallel intermingling cylindrical forming walls along its length. . The raw material inlet is provided in the vicinity of one end of the tubular portion, and a pair of independent and branched substantially cylindrical heads arranged in parallel are provided in the vicinity of the outlet end of the tubular portion. Each outlet end head has a cross-sectional area that decreases along its length and is preferably conical in shape. In addition, a pair of elongated juxtaposed axially rotatable bladed screws are positioned inside the tubular portion of the extruder, and the raw material is moved therethrough. Each screen also includes an elongate portion having a cross-sectional area that decreases along its length, the portion substantially complementing the corresponding tubular head section. A die structure is provided near the outlet end of the tubular head portion for extruding the raw material after passing through the tubular portion. What is important is that each outlet end screw section having a reduced cross-sectional area extends into and is substantially supplementally received by a corresponding head section, which is a tubular section. A bearing-like support is provided for each screw near the exit end of the. As a result, when the raw material passes through the tubular portion of the extruder, the raw material is divided into independent and juxtaposed non-connecting flows, and each raw material flow provides a substantially uniform flow around the adjacent screw and Support, and thus the screw is positioned and pivoted in the split stream of feedstock. That is, the extruder of the present invention provides a bearing support for each screw near the exit or die attach end, which effectively reduces the tendency for screw separation and wear.

In the preferred form, the pair of extruder screws have interengaging wing means and pivot in the same or opposite directions as desired. The wing means may be single wing or multiple wing and may have a cutting continuum over a length to impede the intake and exhaust action of the screw.

Although various raw materials can be processed or processed by the extruder of the present invention, the extruder is particularly suitable for use in processing crops.

That is, the present invention relates to improvements in a double-screw extruder and extrusion method, and more particularly, to an independent bearing-shaped support for supporting a rotating screw as raw material passes through the apparatus. A complementary interfitting conical screw and tubular section are provided near the exit end of the extruder barrel to significantly reduce extruder wear. In the preferred form, the screws are interengaged along substantially the entire length of the extruder barrel but are distributed within the final conical screw section and are received within their respective complementary barrels. In this case, the material to be processed is separated into juxtaposed, non-continuous flows, whereby it flows evenly around the adjoining screw parts, supporting it, weakening the tendency of the screws to separate and to the wall of the peripheral tube. Abrasion weakens contact. The extruder of the present invention can be used for various crop treatments, but is particularly useful for processing objects that are difficult to process with a single screw extruder such as viscous materials such as soybeans.

Specific examples will be described below.

Referring to the drawings, and particularly to FIGS. 1-5, the extruder 10 has an elongated barrel or barrel 12. The tubular portion has a raw material inlet 14 near the rear end and an orifice die structure 16 limited near the other outlet. Further, the extruder 10 has a pair of juxtaposed elongated substantially parallel stepped screws 18, 20 rotatable about an axis. These screens are provided in the cylindrical portion 12 and have a function of receiving a raw material, that is, a material from the inlet 14, transferring the raw material along the longitudinal direction of the cylindrical portion, and discharging the raw material through the die structure 16.

More specifically, this tubular portion 12 is a tubular inlet head portion 2
It has two, three intermediate tubular head sections 24, 26, 28 and a final tubular outlet head section 30. Each of these head portions 22-30 is made up of interconnected halves, and only their lower portion is labeled 22a-30a in FIG. However, as can be seen from Fig. 2-5, each head portion is similarly struck by the upper half 22.
b-30b is included. The upper and lower halves of each head are bolted through vertical holes 32 provided in the side edges of the halves. Further, as shown in FIG. 1, these end portions are aligned with each other and end flange structure portions with holes provided at both ends of each head are connected by suitable connecting bolts 34.

The interconnected heads that make up the overall barrel 12 serve to form an internal annulus providing laterally aligned elongated parallel longitudinally interconnected conical cylinders 12a, 12b. Each screen 1 as described below
We accept 8 and 20. Further, the inner wall of the tubular head 22-30 has elongated slidable upper and lower saddle portions 35 having a substantially V-shaped cross section between the zones 12a and 12b as shown in FIG.
have. These walls are smooth spirals with long ribs extending inward.

The inlet head section 22 and the intermediate head sections 24-28 are mostly known. However, the outlet head 30 is configured to provide a pair of independent, generally tubular, juxtaposed head portions 36,38. Each head section 36, 38 has a decreasing cross-sectional area along its length and preferably a conical section. For this reason, the outlet head portion 30 has a pair of convergent arch-shaped outer walls 40 along the central arch-shaped wall 44,
42 are included. The central arched wall 44 has a pair of arched converging surfaces 46,48. These convergence surfaces 4
6, 48 have disappeared in the respective opposite outer walls 40, 42. The wall structure of head portion 30 thus acts to define a pair of laterally aligned generally cylindrical frustoconical head portions 36,38. Head portion 36 includes wall 40 and surface 46.
While head portion 38 is defined by wall 42 and surface 48. With particular reference to FIG. 4, the central arcuate wall 44 effectively acts to form and divide the head portions 36, 38. As a result, the material advancing along the longitudinal direction of the tubular portion 12 is divided into head portions 36, 38.
Accepted inside. The importance of this structural feature is discussed below.

In the embodiment of FIGS. 1-5, the die structure 16 is in the form of a pair of die plates 50, 52 with holes, which plates 50, 52 are attached by bolts 53 to the head portions 36, 3 respectively.
Each of 8 is bolted to the smallest diameter end. Each die plate 50, 52 has a substantially circular shape,
As shown in FIG. 2, it provides an inward flat surface that abuts a corresponding flat surface of an adjacent die. These dies 50, 52 have a series of annularly arranged die holes 54, 56, although other die openings and arrangements are possible. As shown in FIG. 1, the die plate 50 covers a generally circular outlet opening provided by the conical head portion 36, with a die hole 54 communicating with the interior of the head portion 36. Similarly, the die plate 52 covers the outlet end of the conical head portion 38, and the die hole 56 thereof communicates with the inside of the head portion 38.

The screens 18, 20 consist of a series of axially interconnected steps or flight sections that make up the inlet or supply section, the intermediate section and the outlet section of each screen. Thus, this screen 18 has a step or flight in the entrance section 5
8 and an intermediate section 60 and an outlet section 62. Similarly, the screen 20 includes an inlet section 64, an intermediate section 66, and an outlet section 68. Side-by-side screen division 58,
64, 60, 66 and the steps or flights interlock with each other, thus increasing the injection effect of the entire extruder. However, each outlet section 62, 68 is separate from each other when it is attached to and fully received by the corresponding head section 36, 38. At the die exit end of the extruder, the screws 18, 20 are completely separated and not in mutual engagement.

The inlet sections 58, 64 of the screw are double-flighted and the outwardly flared steps or flighted pivots 70, 72 interengage along the entire length of the inlet section. The main purpose of this inlet section is to rapidly carry the feedstock from the inlet 14 and to compress and condition it in the middle section and the outlet section of the extruder.

The intermediate sections 60, 66 of the screw are also double pivots, but the pivots with flight 7 extending outwards.
4 and 76 are pitches shorter than the rotating parts 70 and 72 of the entrance section. However, in other cases, the rotating portions 74 and 76 may have the same pitch as the rotating portions 70 and 72. Still referring to FIG. 1, a total of five axially aligned and interconnected subsections 60, 66 of the screw (i.e., 7 in the intermediate section 60).
8, 80, 82, 84, 86, and 88, 90, 92, 94, 96 in the intermediate section 66). It can also be seen that all of the subsections of the intermediate section have the same pivoting (flight) shape, and that the subsections 82, 92 include obstructions or cutting continuations 90, 100 along their length. . Such cutting continuous parts 98, 10
0 acts to increase the dwell time of the material in the middle section and increase the mixing of the material.

The outlet sections 62, 68 of the screw also have a double pivot and are connected to the corresponding intermediate section subsections 86, 96. Rotating parts 102, 104 of outlet sections 62, 68
Have a somewhat larger pitch than the corresponding pivots 74, 76 of the middle section. It has been found that the above-described pivoting part shapes (i.e. the use of double pivoting parts, pivoting pitches and subsection cutting continuums) are advantageous, but those skilled in the art will appreciate other various pivoting part shapes. One could easily think of what could be used.

In FIG. 1, it can be seen that three continuous leaf-shaped mixing elements are provided along the longitudinal direction of the screws 18, 20. In particular, the mixing element 106 is between the extreme ends of the inlet sections 58, 64 and the rearmost ends of the intermediate sections 60, 66, and the mixing element 108 is a subsection 8 with a cutting continuation of the intermediate sections.
2, 92 and the adjacent subsections 84, 94, and the final mixing element 110 is the intermediate section subsection 8.
It is located between 4, 94 and the subsections 86, 96.

Referring now to FIG. 5, details of the shape of mixing element 110 are shown. As can be seen, four leaf-shaped mixing elements 112 are located in and form part of a part of the screw 18, and likewise four mixing elements 1
14 constitutes a part of the adjacent screen 20.
Each element 112, 114 includes a circular innermost connection and a pair of opposing lobes that provide an outwardly flared outermost flat surface. The mixing elements 112, 114 are positioned relatively laterally adjacent and each element is rotatably positioned so as not to collide with the juxtaposed mixing elements during their rotation.

The mixing element 108 is in all respects equal to the mixing element 110.
The mixing element 106 also has three rather thick leaf-shaped elements on each screen 18,20. Otherwise, this element 106 is equivalent to elements 108 and 110.

Each screw section and the leaf-shaped mixing element described above has a tubular central form and is provided with a suitable elongated central drive shaft 116, 118.
(Figs. 5 and 7). Each drive shaft 116,
118 has a pair of elongate opposed keyways 120 that allow stable mounting of each screw along the length of the shaft. Taps are provided at the outermost ends of the drive shafts 116, 118, and the outermost connection bolts 12
A screw component is fixed in its longitudinal direction on the drive shaft with which 2,124 cooperate.

Each of the screws 18 and 20 is supported near the rear end of the tubular portion 12 so as to rotate in the axial direction. Referring to FIG. 1, seal structures 126 and 128 are provided on the screen. Of course, these screws are supported by known bearings and are rotationally driven by a motor and a reduction gear which are not shown.

In another embodiment, the present invention may provide a variety of screen, die and barrel structures depending on the desired end use. For example, in FIG. 7, a convergent common tubular die spacer 129 is attached to the outlet of the barrel 12 so as to communicate with the outlet ends of the heads 36, 38. A common die plate 130 with holes is provided at the exit end of the spacer 129. When the extruder shown in FIG. 7 is used, the independent raw material streams flowing from the juxtaposed head portions 36 and 38 are combined in the die spacer 129 and then extruded from the perforated die plate 130.

Another illustration according to the present invention is shown in FIG. This is different from FIG. 5 in that it uses circular mixing elements. In particular, side-by-side pairs of circular mixing elements 131, 132 are fixed onto the corresponding drive shafts 116, 118 of the screws 18, 20. Each element 1
The diameter of 32 is larger than the diameter of the corresponding element 131, and each element is configured such that its outer perimeter is close. In use, a circular element can be used with the leaf-shaped mixing elements 112, 114 within a given mixing element.

When operating the extruder 10, the raw material to be treated is fed into the barrel 12 through the inlet 14. Next screen 1
8 and 20 are rotated in the opposite direction or the same direction. As a result, the raw material advances along the longitudinal direction of the tubular portion 12 and the temperature and shearing force of the raw material increase. Mixing elements 106, 10
8, 110 has the function of increasing the mixing of the raw materials and improving the homogeneity of the raw materials. Further, the continuous cutting portion along the lengthwise direction of the screw serves to increase the suction and / or feeding action of the screw and improve the mixing of the raw materials.

As the raw material being processed approaches the exit end of the extruder, the raw material enters the separate head sections 36, 38 and interrupts into the independent juxtaposed flow section of the raw material. At the same time, due to the converging conical section of the head, the separated feed stream is subjected to compressive forces.

An important feature of the present invention is that due to the exit end geometry of the extruder 10, each screw 18, 20 provides a bearing shaped support near the exit end of the barrel 12. The reason for the occurrence of this support is that the separated flow of feedstock through the heads 36, 38 flows around and supports the screw outlet sections 62, 68 rotating within the heads.

Screen 1 at the screen exit sections 62 and 68
The provision of the 8,20 front end bearing-like support structure, together with the known mechanical bearing support at the rear screw end, provides the desired screw support at both ends of the screw. This is different from the cantilever bearing support in the known double screw extruder. To understand the effectiveness of this feature, FIG. 8 is shown. This figure is a schematic view of a known double-screw extruder. In this extruder, a pair of rotatable screws 134, 136
(Rotating in the same direction in the figure) is provided in the tubular portion. As the screws 134 and 136 rotate during operation of the extruder, the high and low pressure regions (in FIG. 8, respectively + and +) corresponding to the regions in which the screws engage each other.
And-) are generated. These high and low pressure areas result from clogging of the feedstock within the interengaging areas of the screw. And such pressure generation in the interengaging area of this screw is indicated by arrow 138,
An outwardly directed resultant force vector such as 140 is produced. As can be readily seen in FIG. 8, this vector acts to pull adjacent screws 134, 136 from each other. For this reason, the screw may come into contact with the vicinity of the wall surface of the cylindrical portion at the portion described as "wear surface" in FIG. The tendency of screw separation in such known double screw constructions of extruder screws has resulted in wear engagement with the barrel wall and has been a longstanding problem in known similar devices. During the operation of previous double-screw extruders, in some cases, such wear contact could be heard as rounded down. However, in the double screw extruder of the present invention, the front and rear ends of the screw are supported by the bearings, and such a serious problem of wear (and accompanying problems of machine stoppage and cost of machine elements) is significantly reduced. did.

Further, during the passage through heads 36, 38, the problem of speed differentials in the double-screw extruder was greatly reduced by the raw material flow separation process into each adjacent channel.
As mentioned above, one problem with previous dual-screw extruders is that the cross-sections of the machine (ie, central and peripheral areas) tend to cause the feedstock to pass through at different speeds. Ivy. However, due to the separation flow according to the invention, this speed difference problem has been improved. At the same time, the conical outlet sections 62, 68 rotate within the conical head sections 36, 38 so that these outlet sections 62, 68 positively transfer the feedstock towards the final die, thus No stagnation and charring problems occur. But the exit head section 3
Due to the conical shape of 6,38, the conversion of mechanical energy into heat often occurs.

The extruder of the present invention can process various raw materials. This extruder is currently believed to be most effective for use in crops such as wheat, corn, soybeans, rice, and oats, but the vast majority of materials previously processed in extruders are extruded. It can be used on a machine. Generally, the extruder 10
In the case of normal work of, the screw 18, 20 is about 100 ~
It is rotated at a speed of 500 rpm, and the temperature condition inside the cylindrical body 12 is maintained in the range of about 100 to 350 ° F. The pressure condition in the cylinder 12 is maintained in the range of 10 to 1,500 psi.
When processing crops as described above, these crops are usually mixed with some water before being fed to the extruder.
Also, the total moisture content of the materials fed to the extruder 12 is generally about 12-35% by weight. However, those skilled in the art
It will be appreciated that the above numbers are merely exemplary and that these may vary widely depending on the characteristics of the original raw materials used and the characteristics of the final product desired.

[Brief description of drawings]

FIG. 1 is a cutaway sectional view showing a cylinder and a screw of a preferred double-screw extruder according to the present invention, and FIG. 2 is an end elevation view of a die, that is, an exit end of the extruder shown in FIG. Fig. 3 is a view similar to Fig. 2 showing the extruder with the end die plate removed, and Fig. 4 is a broken vertical sectional view taken along the line 4-4 in Fig. 3, showing one of the screws. 5 is a cross-sectional view taken along line 5-5 of FIG. 1, in which an elliptical leaf-shaped mixing element is attached, and FIG. 6 is a view similar to FIG. FIG. 7 is a partial sectional cutaway view showing the outlet end of an extruder according to the present invention, in which a conical die spacer and a common die plate with a hole between the ends of adjacent extruder screws are used. And Fig. 8 is a schematic view of a known double-screw extruder, in which the extruder screen is drawn. It is a diagram vector and this indicates the occurrence of excessive wear which occurs to the extruder to do so. DESCRIPTION OF SYMBOLS 10: Extruder, 12: Tube part, 14: Raw material inlet, 16: Orifice die structure, 18, 20: Screen, 22:
Inlet head section, 24, 26, 28: intermediate head section, 3
0: exit head part, 35: saddle part, 36, 38: head part, 40, 42: arch-shaped outer wall, 44: central arch-shaped wall, 46, 48: convergent surface, 51, 52: die plate,
54, 56: Die hole, 62, 68: Exit section, 98, 1
00: continuous cutting portion, 106, 108, 110, 112,
114: mixing element, 116, 118: central drive shaft, 12
9: Die spacer, 130: Die plate, 131, 1
32: circular mixing element

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Bobby Davryu Hawk, Kansas State 66534, Sabesa, Virginia Street 603 (72) Inventor Timothy Earl Harter, Kansas State 66534, Sabesa, West Main Street 1553 (56) Reference JP-A-51-2770 (JP, A) JP-B-55-93 (JP, B2)

Claims (8)

[Claims] 1. A double screw extruder 10 having an inlet head portion 22 supporting one end of each screw.
And an outlet head portion 30 supporting the orifice die structure 16 at the downstream end on the other end side of these screws.
And intermediate head portions 24, 26 arranged between the downstream end of the inlet head portion 22 and the upstream end of the outlet head portion 30,
28, and the inlet head portion 22 is provided in these head portions 22 to 30.
There is a pair of axially parallel tubular cavities communicating from the outlet head to the outlet head 30 and rotatably accommodating the screws, these cavities at the inlet head 22 and the intermediate heads 24-28. Have substantially the same cross-sectional area and communicate with each other on their adjacent side surfaces, but in the outlet head portion 30 they are separated by a central wall 44 to form a pair of independent head portions 36, 38, These head portions 36 and 38 are the same as the outlet head portion 3.
0 has a cross-sectional area that decreases from the upstream end to the downstream end, and the raw material inlet 1 is provided near the inlet head portion 22.
And a pair of elongated, side-by-side, axially arranged axially arranged barrels for moving the raw material introduced from the raw material inlet 14 towards the outlet head portion 30. Of the rotatable rotation part-equipped screws 18, 20, the rotation part of one screw is intermeshed with the rotation part of the other screw by meshing with a predetermined depth. Inlet head portion 22 and intermediate head portion 24 to
An elongated generally frustoconical outlet end screw section 62 having a generally equal cross-sectional area at 28 but a portion located within said outlet head portion 30 having a decreasing cross-sectional area along its length. , 68, wherein the length of the outlet screw sections 62, 68 is greater than the maximum diameter of the outlet screw sections 62, 68.
8 and 20; the outlet end screw sections 62 and 68 have spiral rotating portions 102 and 104 around them, one of the rotating portions being engaged by a predetermined depth to the other outlet end screw section. Interlocking with the pivoting portion of the end screw segment, which in turn is progressively forward from the rear end of the end screw section until the pivoting portions are completely separated from each other at a point rearwardly away from the outlet end of the barrel. A respective outlet end screw section 62, 68 having a reduced number of pivoting portions extending to the outlet end screw section 62, 68 into and through the head section 36, 38 during operation of the extruder. As the raw material passes along the inner peripheral wall surfaces of the head portions 36, 38, the head portions 36, 38 are extended into the corresponding outlet end head portions 36, 38 for supporting the other ends of the screws with rotating portions. And each of the outlet end screw sections 62, 68 received by the head portion; an orifice die structure 16 for pushing the raw material introduced from the raw material inlet 14 through the outlet head portion 30; Means for placing the die structure 16 in a spaced relationship to the front end of the exit end section near the exit end, the means for mounting the die structure 16 between the front end of the exit end section and the die structure 16. An extruder having a spacing of less than one length of one of the generally frustoconical exit end sections for mounting the die structure 16. 2. The die structure 16 comprises a pair of independent perforated die plates 50, 52, each die plate secured to the outlet end of a corresponding tubular head portion 36, 38. Extruder. 3. The die structure 16 includes a common tubular die spacer 129 having a first end and a second end, the first end secured to and in communication with an outlet end of the tubular head portion, and a hole. The extruder according to claim 1, wherein the attached die plate 130 is fixed to the second end of the spacer. 4. The extruder according to claim 1, wherein the longitudinal axes of the screws 18 and 20 are parallel to each other. 5. The extruder according to claim 1, wherein the rotating portion of the screw is cut off to prevent normal pumping action provided by the screw. 6. The extruder according to claim 1, wherein the screws 18 and 20 rotate in the same direction. 7. The extruder according to claim 1, wherein the screws 18 and 20 rotate in opposite directions. 8. A rotatable mixing element 106, 10 positioned along the length of the screw 18, 20.
The extruder of claim 1 including 8,110.