Idler Rollers

In addition to the upward blown film there is also the downward extrusion. It allows the tube to be quenched rapidly in a water bath after which it is collapsed as a layflat for passage over nip and idler rollers. 

Belt conveyors belt speed 1 m/s handling solids of density 1.6 Mg/m with steel welded frame, head and tail pulley, troughing idlers, roller bearings, cold rolled steel shafters, four ply, 28 oz belt excluding motor, drive and supports. FOB cost = 21000 for the product of (solids capacity, Mg/h) X (length, m) = 10 with n = 0.20 for the range 5000-5 X 10. L+M = 1.7-2.7. L/M = 0.3. 

When the bubble has cooled sufficiently, it is flattened in a collapsing frame and pulled through a set of nip rolls to its top. From there, the layflat film is guided over several idler rollers to the winder where it is rolled up over a core. 

FIGURE 20.1 Schematic representation of melt spinning setup (1) extruder drive, (2) extruder, (3) hopper, (4) screw, (5) manifold, (6) static mixer, (7) metering pump, (8) metering pump drive, (9) spin pack, (10) mesh filters, (11) distributor, (12) spinneret, (13) cross-flow quench chamber, (14) freshly spun yam, (15) godet, (16) idler roller, (17) friction-driven winder, (18) yarn bobbin. 

Figure 4.31 Application of 4-point tip nozzle for moulding of an idler roller from PA 66 Reproduced with permission from EOC Normalien)...

Inspecting installation and alignment of trough idler rollers and return idler rollers... 

Water Quench. The water queneh east film process (Fig. 8.9) is similar in concept to the chill roll process and uses similar downstream equipment. A water bath takes the place of the chill roll for film cooling, and by cooling both sides of the film equally, it produces a film with slightly different properties compared to chill roll cast film. The extruder s slit-die is arranged vertically and extrudes a melt web directly into the water bath at elose range. The film passes under a pair of idler rollers in the bath and, for any given rate of extrusion, it is the rate of downstream haul-off that regulates film drawdown and finished thickness. 

Very low ACN (< 27%) containing NBRs are used for hydraulic hoses, idler rollers for low temperature, and refrigerator hoses. Low ACN (27 to 31%) containing NBRs are used for o-rings, injection molding, seals and gaskets, industrial belt covers, hoses, and hydraulic hoses. 

FIG. 21-4 Belt -conveyor loading details, (a) Typical sldrt-plate design and dimensions, (h) Pad belt and special roller-bearing idlers for heavy-duty loading Stephens-Adamson Division, Mlis-Chalmers Corporation.)... 

Shaft Centers. It can be readily seen that on any chain drive the minimum center distances must be more than one-half the sum of the diameters of the two sprocket wheels. Experience has shown that best results are usually obtained when the center distance between shafts is 30 to 50 times the chain pitch. Forty times the chain pitch is about normal, and 80 times the pitch is maximum. In highly pulsating loads, 20 to 30 times the pitch is more nearly the correct center distance. Center distances of 10-12 ft are permissible with finished steel roller chains operated at moderate speeds without the use of idlers. On distances greater than this, an idler should be used to eliminate the possibility of swaying or flopping, which may cause the chain to jump the sprocket. When idlers are used, they should be placed on the slack strand of the chain. The number of teeth in the idler should be the largest possible and preferably not less than the number in the smaller sprocket of the drive. 

Belt conveyors are the most commonly used type of equipment for the continuous transport of solids. They can carry a wide range of materials economically over long and short distances both horizontally or at an appreciable angle, depending on the angle of repose of the solids. A belt conveyor consists of an endless belt of a flexible material, supported on rollers (idlers), and passing over larger rollers at each end, one of which is... 

Some drawbacks to the weigh belt are that it is a zero-reference device and thus needs frequent calibration (re-zeroing). Buildup on the belt and rollers affects accuracy and operation, as does belt tension and dusty or floodable materials. Flexible connections are required to isolate the feeder from upstream and downstream equipment, unless the belt feeder/weigh idler concept is used. 

Belt idler A roller, usually of cylindrical shape, which is supported on a frame and which, in turn, supports or guides a conveyor belt. Idlers are not powered but turn by contact with the moving belt. 

Return idler The idler or roller underneath the cover or cover plates on which the conveyor belt rides after the load that it was carrying has been dumped at the head section and starts the return trip toward the foot section. 

Alternative designs to the conventional belt conveyors include steep-angle and vertical conveying systems with the surface worked into pockets formed by high sidewalls and scoop cleats, and hose-belt or tube conveyors in which the flat belt is shaped by means of concave idlers and guide rollers to overlap the belt edges (Bahke, 1991). 

Belt perches. Where loose pulleys or idlers are not practicable, belt perches in form of brackets, rollers, etc., shall be used to keep idle belts away from the shafts. 

The most common type of chain tightener is an idler sprocket mounted on an adjustable bracket, either manually adjusted or spring loaded. Rollers, shoes, and vibration dampeners are also used for regulating chain excess tension. The idler design and installation should be capable of providing enough adjustment to remove two full pitches of chain. This avoids the need for a less desirable offset link. 

Idler sprockets for roller and engineering steel chain drives wear in a different way. There is not much pressure on the working faces of the teeth on an idler sprocket. So idler sprockets usually wear at the bottom of the tooth space. A badly worn idler sprocket for roller chain is shown in Figure 15-2. When the tooth space is worn deeply enough, the chain rollers may bind against the tooth tips as they enter and leave the idler sprocket. 

FIGURE 15-2 Worn roller chain idler sprocket. 

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