Horizontal feed screw

Upper Feed Hopper Collects virgin and recycle product Horizontal Feed Screw Controlled feed... 

Fig. 6 Twin horizontal feed screw system with vacuum deaeration. (Courtesy of Alexanderwerk Inc.)...

Miller indicated that a multiple horizontal feed screw design system provided a more uniform powder distribution across the rolls in area and volume than a single vertical feed screw system. This concept applied to either the vertical or the horizontal single feed screw systems. ... 

When the feed screws are positioned perpendicularly to each other, they are generally designated as the horizontal feed screw (HFS) and the vertical feed screw (VFS)... 

Fig. 6.2-63 Pharmaceutical compaction/ granulation system with vertical roller arrangement, horizontal feed screw, and granulation by two-stage milling (courtesy Alexanderwerk, Remscheid, Germany)...

Fig. 6.2-61 depicts two typical designs and arrangements of roller presses for pharmaceutical applications. As mentioned above, small presses in particular are sometimes equipped with rollers one-above-the-other (alternative a2). In this case, the force feeding screw is installed horizontally. It is often said that this design allows for better de-aeration as shown in Fig. 6.2-62. In this diagram, (1) is the raw blend, (2) is a special hopper equipped with a rotating flow stimulator, a separate de-aeration chamber, which is also used for feeding recycle (3) and additives (if applicable), and air removal port (4), (5) is a vacuum pad option for further direct de-aeration from the horizontal feed screw, and (6) is the recirculation of powder leakage [B.13b, B.48, B.97].

The newly designed equipment involved a compactor fitted with two horizontal feed screws, which featured vacuum deaeration. Specifically, the roller compactor was equipped with a conical storage hopper containing a variable speed agitator. Bulk powder was fed directly from the top of the hopper to the top of twin horizontal auger feed screws, which directly transported the powder to the nip roll area (13). Top and side views of the design features are shown in Figure 17. ... 

The use of multinozzle injection machines. In general, this type of machine has a horizontal reciprocating screw that feeds four injection nozzles each connected to a single cavity mold thus minimizing waste. However, one concern with this approach is the need to have the mold accurately lined up (the top and bottom surfaces of the mold will be in the vertical plane) to eliminate compound leakage at the nozzle/mold interface. 

In the A-R type, the feed screws end in blades that rotate along the horizontal axis but force the wet mass through a screen-placed radial or cylindrical around the blades (Fig. 5). The A-R extruders have somewhat conical extrusion heads resulting in an overflow, i.e., a certain amount of feed material is pushed axially between the screen and extrusion head at the front instead of radially through the screen area. A greater open area of screen results in a higher and faster throughput. However, the hardness... 

Pietsch described, in Fig. 5, modern feed screw system designs (A) depicts vertical force-feeding screw with slightly tapered end, (B) an inclined feed screw, (C) a vertical tapered and blade angled feed screw, and (D) horizontal (single or dual) straight feeder screw(s). ... 

Guigon and Simon, in 2001, showed a similar phenomenon using a horizontal single feed screw without vacuum deaeration when compacting sodium chloride. ... 

In several experiments, Miller studied the effects of using horizontal twin auger feed screws under partial vacuum (Alexanderwerk Inc., Horsham, Pennsylvania, model 50/75 compactor). The feed powder was vacuum deaerated just before roller compaction. The experimental design showed that the compactor s deaeration feed system significantly increased compaction output and minimized powder leakage when compacting very low density blends (<0.35 gcm ). ... 

The Alexanderwerk Inc. roller compactor (Fig. 18) is modular designed with a horizontal twin feed screw... 

The Fitzpatrick Co. roller compactor (Fig. 20) features two feed screws in series one horizontal and the second vertical. This system is designed to transfer powder bulk into a set of cantilevered rolls positioned in the horizontal mode one is fixed, the other floats. Operator interface allows for on-line monitoring and controlling feed screw speeds, roll pressure, and roll gap. Features such as on-line help and diagnostic functions, maintenance, and calibration screens are displayed. All functions are interfaced and adjustable by PLC for process control and report generating. The machines have vacuum deaeration and roll cooling capabilities. The sizing unit is separate from the compactor and is either a rotor bar or a hammer mill. 

The feed-screw design can vary (i) vertical straight and lightly tapered screw feeder (ii) slight inclined screw feeder (iii) tapered vertical screw feeder and (iv) horizontal straight feeder screw. The screw design requirements will depend on the flow characteristics of the precompacted material. Powder feed variability can lead to undesirable outcomes, namely excessive fines and irregularly compacted ribbons that can lead to broad particle size distributions. 

As an alternative, the screw and barrel (plunger, barrel, and stuffing mechanism) are horizontal, feeding into the horizontally positioned closed mold through a sprue bushing at the parting line of the closed mold (Fig. 6.21). 

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