Salient Features of Apron Feeders
Frame: The main frame of the feeder is fabricated out of rolled steel structural members, heavily ribbed and supported to impart rigidity and strength to withstand impact without any appreciable deflections. Welding is done by qualified and experienced welders, under close supervision.
Pans: Overlapping type fabricated steel pans or cast manganese steel pans are used depending on the service conditions to ensure minimum spillage of materials through overlapping portion.
Chains: Depending upon the severity of application either heavy-duty crawler chains or link plate roller chains are used. Crawler chains are used for heavy and extra heavy-duty application. These chains have high static breaking load and are lubricated for life. High surface hardness ensures maximum wear resistance. Pans are torque tightened with the chains through high-tension bolts. For comparatively lighter and less critical application link plate type roller chains are used. Roller chains are made of heavy gauge formed steel, flanged and drilled for pan attachment. Chain links have hardened and precision ground brushes, pins and rollers to give long trouble free service. Depending on width and duty there may be two or three strands of chains.
Carrying Rollers: Crawler type chains are supported and guided on the main frame by carrying rollers. These rollers are lifetime lubricated. Special seals ensure a perfect sealing joint for lubricant, which is contained in an approximately dimensioned cavity, guaranteeing proper lubricant circulation and the rollers do not require further lubrication. In the loading zone, rollers are closely spaced and sometimes-special rubber pads are provided below the rollers’ seating to absorb impact from falling material. For link plate type roller chains, normally no carrying rollers are used. Chain rollers roll over the rails/ square bar, thus supporting the chain.
Impact Rails: Depending upon feeder width one or two impact rails are provided below the pans. Impact rails prevent permanent pan deformation during severe impact, but provide ample clearance between rail and pan during normal operation.
Sprockets: Heavy duty segmented type sprockets with excellent wear resistance are fastened to the sprocket hubs through high-tension fit bolts. These sprockets are generally procured from the crawler chain manufacturer for better compatibility. Cast steel sprockets are also supplied which are machined to close tolerances. Teeth may be flame hardened to suit the duty conditions. The sprockets are keyed to EN-8 or superior shafts.
Bearings: Head, tail and counter shafts are supported on liberally sized babbit bearings/special roller bearings, housed in cast iron pillow blocks.
Tensioning Device: Generally a screw-type tensioning device is provided. However, hydraulic tensioning may also be provided optionally.
Drive: The head shaft is normally driven by counter shaft through a pair of machine cut steel spur pinions and gears. The counter shaft may be driven by chain or gear drive depending on duty required, by a motor and reducer. The gear drives and chain drives are provided with suitable guards. A variable speed drive may be supplied as an option.
Lubrication: All bearings are provided with grease fittings and can be manually greased. Automatic centralised lubrication may be provided as an option.