Eyelink belts

Sprockets
Generally, eyelink conveyor belts are driven directly on the eyelinks by means of specially developed drive sprockets. For DO belts these sprockets are provided with block teeth. In the case of DL belts the sprockets are constructed such that they exactly match the profiles at the underside of the belt. In case of belts with a large cross pitch (centre-to-centre distance of eyelinks) one could consider to place sprockets that are directly driven on the cross rod instead of on the eyelinks. Generally the sprockets are placed at both sides and under each row of plate links. The width, the number of teeth and the material of the sprockets are determined on the basis of the conditions of use.

When a construction of drive sprockets is applied in a freezer, sprockets with special toothing are used. In order to prevent the accumulation of ice, the so-called ‘ice-crusher’ sprockets are used. The special toothing limits the accumulation of ice to the minimum.

Sprockets are available in steel, AISI 304 (WS 1.4301), AISI 316 (WS 1.4401), PA6G and POM, or in other materials on request or on advice. An example of a stainless steel sprocket is featured below.

Chain sprockets
Eyelink belts can also be produced with chains, whereby the chain fulfils a driving function. Especially when the belt has to perform a negative bend, as is the case with many applications for freezing or blanching, and for ascending belts. In those applications the side-sprockets are replaced by chain sprockets belonging to the chain applied.

In this case, too, the rule applies that for bigger constructions chain sprockets will be placed in combination with a roller.

In all applications with chains a negative bend of the belt can easily be achieved by means of chain sprockets or wear strips of the hollow pin roller chain. Twentebelt prefers the use of sprockets with at least 12 teeth. This is based on the fact that with this number of teeth the so-called polygon effect will exert hardly any influence on the belt run. If the length and the load of the belt are moderate drive sprockets with a minimum of 8 teeth might be used. The ultimate determination of the necessary number of teeth depends on factors like width, length, load and running speed of the belt.

Cage rollers
Broad and heavily loaded eyelink conveyor belts are preferably driven by rollers right across the width of the belt, cage rollers in most of the cases. The straps of the roller regularly drive all the eyelinks of the pitch, which is conducive to a longer life span of the belt and also leads to a regular wear pattern.

Disc rollers
If there is a risk of accumulation of filth or ice, disc rollers should preferably be used. On a multiple of the cross pitch these rollers are provided with discs. These discs can be produced in different ways, so that different properties can be created:

– Drive on the cross rod
– Drive on the cross rod with a ‘lifting function’, where the teeth protrude through the belt and lift the product for discharge.

Tube rollers
In the grooves of tube rollers with replaceable strips, plastic or soft-metal strips are placed. In case of tube rollers with replaceable teeth, the teeth are not welded but screwed in. This construction has three advantages:

– The tube construction limits deflection.
– The drive components are replaceable.
– The roller is reversible, which makes a second life cycle of the strips and the teeth possible, before they must be replaced.
In general, tube rollers drive long, broad and heavily loaded belts.

Idler
As for the return shaft there is a choice between toothed or smooth wheels or rollers. In principle, toothing only has a function in case of accumulation of ice or filth. Toothing on the return shaft consequently has no drive function. Generally, in small installations one prefers to provide the return shaft with toothed wheels. When, however, a cage roller was chosen to drive the belt, a smooth roller will be chosen for the return shaft. An exception to this is a drive with cage rollers and chain wheels, whereby the same construction is used as a return roller.

If provided with one tooth per pitch the rollers are one-directional and thus only to be used for drive or for return. Rollers with double strips can be used for both drive and return, if the installation is designed for this purpose.