Blister ring

FIG. 18-50 Intermeshing corotating twin screw extruder (a) drive motor, (h) gearbox, (c) feed port, (d) barrel, (e) assembled rotors, (f) vent, (g) barrel valve, (h) kneading paddles, ( ) conveying screws, (/) splined shafts, (k) blister rings, (APV Chemical Machinery, Inc.)... 

Figure 8.23 Schematic of blister ring mixers a) a blister mixer positioned in a metering section, b) blister section positioned at the discharge end of the screw near the tip, and c) the cross-sectional view showing the region of annular flow between the screw and barrel wall (courtesy of ieff A. Myers of Robert Barr, Inc)...

Fig. 24. Dispersive mixing sections for use in single-screw extruders (a) blister ring, (b) Union Carbide mixing section, (c) Egan mixing section, (d) Dray mixing section [148]...

Fig. 10.10 (a) Top and side views of a pair of full-bore blister rings (orifice plugs), and (b) schematic of the Todd barrel valve and barrel cross sections in the fully open and closed positions there is a bypass channel in the barrel immediately above the intersection of the blister rings and the barrel valve is rotatable in this bypass channel to vary the restriction of flow. [Reprinted by permission from D. B. Todd, The APV (Baker Perkins) Systems, in Plastics Compounding— Equipment and Processing, D. B. Todd, Ed., Hanser, Munich, 1998.]... 

Mixing screws — S-shaped kneader, Eagle mixing. Turbine mixing, Cohen double-wave, or Maillefer screws with pin-, blister ring-, fluted-, barrier-screw. Dynamic Extentional Flow Mixer (DEEM), etc. 

The main difference in this mixing section is that the outlet channel is open at the start of the mixing section. Thus, not all material is forced over the barrier clearance. Therefore, this mixing device will not result in a uniform shear history of the material. An extreme form of a fluted mixing section is the annular blister ring see Fig. 8.69. 

The annular blister ring is simply a smooth cylindrical screw section with a small radial clearance. All the material has to pass through this clearance to exit from the extruder. Since no positive drag transport takes place over the barrier clearance, the... 

There are several types of dispersive mixing sections blister rings, fluted mixing sections, and planetary gear extruders. 

Fig. 2. Intermeshing corotating twin-screw extruder A, motor B, gear box C, feed port D, clam shell barrel E, vent port F, screw shafts G, conveying screws H, kneading paddles I, barrel valve and J, blister rings. Courtesy of APV Chemical Machinery Inc.

Blister ring A raised portion of the root between flights of sufficient height and thickness to effect a shearing action of the melt as it flows between the blister ring and the inside wall of the barrel. 

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