Cheek plates

Springs and Cups 19. Cheek Plates (top) 28. Eccentric Shaft Bearing Bush (top)... 

Swing Jaw Shaft 19A. Cheek Plates (bottom) 29. Swing Stock Bush... 

In single-row presses the cheek plates may cause substantial differences in... 

Sealing the roll nip A successful roll press operation requires a loss-free buildup of pressure in the nip and a minimum leakage of uncompacted material. To provide a reasonably closed volume in which these conditions are fulfilled, cheek plates (Figure 282) seal the sides of the rolls. While designs vary with the manufacturer, cheek plates are basically heart-shaped steel plates which are kept in a close position to the sides of the rolls. Sometimes special shoulders are provided forming a simple labyrinth. 

Cheek plates are wear parts and, therefore, must be replaced or repaired in regular intervals. Often, exchangeable hard-metal wear plates are provided at the point of highest pressure and wear (Figure 282). In particular, larger modern machines are equipped with cheek plates that can be easily replaced without dismantling other parts of the machine and are adjustable from the outside of the frame " to correct, within limits, wear. 

Figure 282. Schematic representation of simple cheek plates used to seal the nip between rollers...

Figure 283. Diagram depicting sealing of the nip between two rollers (1) with cheek plates (2) and feeder base (3). Also shown are escape paths for displaced gas (see also Figure 249)...

Figure 288(a) depicts on the left side the conditions in a machine with a narrow roll face and on the right side the wide-faced machine, both with gravity feed. Since there is little cross-flow in the nip the starved feed conditions in the roll border zones result in less compaction and, in extreme cases, excessive leakage at the cheek plates. It is obvious that this effect is more noticeable if the roll face is narrow because, although the absolute amount of less densified border zone material is constant for a given material, roll diameter, and feeder geometry, the relative proportion is smaller if wide-faced rolls are used. 

Cheek plates (for design and more detailed descriptions see below), the heart-shaped pieces sealing the side of the nip between the rollers, can not be in rubbing contact with the rollers as excessive wear would take place and the constant friction, which is aggravated by the presence of fine powder particles, causes the rollers and the cheek plates to quickly become red hot. Rather, well adjusted cheek plates have a finite clearance which is selected such that the leakage of fine material is minimized. In this... 

To overcome the above mentioned problems, wide rollers are subdivided into two or more rings with one or more gap in between where cheek plates are arranged and deaeration can take place. 

With these machines, the shafts are supported in a frame and the rollers are mounted on the front of that frame. Fig. 8.144 shows four examples. Because the feeder, the rollers, the cheek plates, and the nip are relatively freely accessible from the outside, these machines are used for frequently changing small applications, for development work, and in the pharmaceutical industry. 

Particularly if fine nutrient powders or carriers for agrochemicals are processed, deaeration, which is the removal of air from the densifying mass, requires special design and operational considerations. In machines with large production capacities this includes the split roller design, which is characterized by two separate compaction rolls on each shaft with a gap in the middle that provides additional venting of air at the center cheek plates. 

Elimination of screen (10) Since fines separated at this point amount to only 10% (mostly leakage from the compactor cheek plates) screen (10) may be eliminated. However, crusher screen (13) and/or primary granulator (22), if applicable, may be less efficient. 

As silicones are relatively soft materials at room temperature, often with little nerve or green strength, it is necessary to equip mills with close fitting cheek plates and a nylon faced scraper blade for removing the band of material during cross-blending and final sheeting (Fig. 3). 

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