Rotor doubled-flighted

Other Kobe Steel patents followed. In a February 1981 US patent application, Inoue et al. [51] described a pair of juxtaposed double flighted rotors. In an August 1986, patent application Asai and Hagiwara [52] described a new double flighted rotor design. The intention was to increase the rotor tip flight clearance to values greater... 

Figure 3c. Optical micrographis with various fill factors (double-flighted rotor mixer).

White [23,24] observed the circulatory flow behavior using markers with flow visualization technique in the R-R handed screw and double-flighted rotors mixer (Figure 8). This makes possible measurement of the circulation time as a criteria of mixing. Since the flow visualization experiments have limitations in observing the overall flow motion in the mixer, the following experiment was carried out to determine the distribution of elastomers. 

From these results, the circulatory motions that occur are R-R screw rotors and double-flighted rotor. But in the R-L screw rotors, the flow motion is pumping forward like twin screw extruders. 

The circulation time at a rotor speed of 5 rpm is plotted as a function of fill factor for the R-R handed screw and double-flighted rotors. This is shown in Figure 11, which indicates that a void region shortens the circulation time. If there are no voids, the flow in the rotor is inhibited, leading to poor mixing. The circulation time for screw rotors is shorter than that of double-flighted rotors. 

Figure 7. Maximum and steady state as a function of fill factor, (a) R-R screw rotors, (b) R-L screw rotors, and (c) Double-flighted rotors.

Figure 10c. Computed isobars on double-flighted rotors from Kim et al. theory together with experimental results of this paper [21].

Measurement of the circulation time in the mixer was carried out to characterize the distributive mixing. The results indicated that void region shortens circulation time. The circulation time of R-R screw rotor is shorter than that of double-flighted rotor. The shorter circulation time represents a good distributive mixer. 

Velocity vectors in a double-flighted co-rotating twin screw extruder at different rotor positions... 

In the 1950s a new company based in Cleveland, Ohio, began to manufacture internal mixers. This was Stewart Bolling and Company. Their early machine was described in a February 1954 patent application [31]. The basic design was very similar to Banbiuy s 1916-1917 machine described earlier. The mixer contains a ram and two double flighted rotors, which pump in opposite directions as in Banbury s design. 

These studies were continued by Min [46] who compared rotors with R/L and R/R screws with Banbury double-flighted rotors and tapered rotors. She found that R/L screw rotors combinations both pumped rubber in the same direction. No inter-rotor material transfer was observed. R/R rotors, Banbury double-flighted rotors, and tapered rotors circulated the rubber around the mixing chamber. 

Their results for R/R screws and double-flighted rotors are summarized in Fig. 9.13, where circulation time is presented as a function of fill factor for both rotor designs. The screw rotor circulates the rubber in the mixing chamber more rapidly than the double-flighted rotor design. 

The distribution of rubber on the two rotors suggests the circulating flow described above (see Fig. 9.14). Griffith et al. [50] reported similar studies of double-flighted rotors. 

Figure 9.14 Distribution of cured rubber in double-flighted rotors at various fill factor [48,49]...

Basically it is found that material in the internal mixer chamber for double- and four-flight rotors circulated around the mixing chamber (Fig. 21). 

TABLE III Flow Characteristics of Double- and Four-Flight Internal Mixer Rotors from the Patent Literature... 

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