Chain still going strong after nearly 600 years

Chains were probably conceived as early as the 15th century, when Leonardo da Vinci produced a series of sketches illustrating the basic principle.

Chains were probably conceived as early as the 15th century, when Leonardo da Vinci produced a series of sketches illustrating the basic principle.

Some of the drawings closely resemble the actual form of modern day roller chain.

However, like so many of Leonardo's ideas that were ahead of their time, it wasn't until much later - the late 19th century when bicycles became popular - that chains really started to be used on a large scale.

As a power transmission medium, chain is today generally viewed as a mature technology.

This is true if one looks at the general level of technical development, which is targeted on achieving increased operating life, greater reliability and reduced maintenance.

It is not the whole picture, however.

In many areas of chain technology, particularly in respect of conveyor and hybrid plastic/steel chains, there is a genuine product innovation.

Modern manufacturing has produced a whole new set of demands on chain.

Operating environments have to be cleaner and quieter to work in.

Power transmission systems generally have to be smaller while still being able to transmit equal or increased levels of power as the larger systems, which they replaced.

There are other considerations too.

Today, chain is used in precision indexing and conveying tasks.

Such tasks - assembly of PCB boards for example - cannot tolerate the initial levels of stretch, which in many other applications are taken for granted.

While lubrication is still employed with most chain drives, its necessity, especially on the factory floor, is increasingly being called into question by innovations like Tsubaki's new Lambda chain.

Lambda is lube-free yet it offers 7 to 30 times the wear life of standard lubricated roller chain.

It also offers 30% longer wear life compared with previous Lambda series chains, and up to 20 times the wear life of other lube-free chains.

This improved performance results from a construction, which comprises specially sintered, oil impregnated bushings, coated pins and extra durable rollers.

The durable rollers facilitate super smooth engagement on the sprocket for longer periods of time.

This significantly reduces sprocket wear.

Moreover, the smooth articulation of chain and sprocket reduces power transmission losses by a high order.

Added to this, the new Lambda series can withstand up to 25% higher power ratings when compared with the previous series: this as a result of an improvement in the maximum allowable load of the connecting links and two-pitch offset links.

Lambda can be used in a wide range of industrial environments.

In addition to applications in general engineering, it is especially suitable for "clean" industries like food processing, printing, packaging and textiles, where lubrication is neither practical nor desirable.

Lambda is now in its third incarnation from the original generation launched back in 1988.

As mentioned earlier, maintaining an accurate conveying pitch is essential to index drive equipment used in such applications as inserting components on integrated circuit boards, film wrapping, component cutting and packing, and injecting lines.

However, standard chain undergoes wear elongation resulting from the constant sliding friction that occurs between the chain pins and bushings.

This causes chain pitch discrepancies, which affect product quality, necessitate continual chain adjustment, and make frequent replacement inevitable.

The design of Tsubaki's revolutionary Bearing Bush chain overcomes these problems.

The chain incorporates uniquely designed needle bearings which eliminate almost all pin-bushing wear by converting sliding friction into rolling friction.

The rollers in the needle bearings separate the pin and bushing surfaces which rub against each other causing the wear in standard chain.

They roll easily along each other causing the wear in standard chain.

They roll easily along both surfaces drastically reducing friction and eliminating wear.

Tests conducted using standard RFN Bi-Pitch Bearing Bush chain to a length of 3m, have produced a consistent stopping accuracy of +/-0.5mm.

In other applications HG series chains, with ground attachments, have been reported as attaining accuracies of +/-0.2mm.

Another innovation in the conveying area is BRCC bearing roller conveyor chain.

This employs precision roller bearings inside the chain rollers to raise the maximum allowable roller load to three times that of standard conveyor chain.

The increased capacity provided by the rollers enables users to select chain sizes up to two times smaller than normal, thus producing savings on power and on the cost of chain and accessories such as sprockets and drive motors.

Using cylindrical roller bearings inside the chain rollers also reduces the frictional coefficient of the chain to 0.03, about one third that of conventionally constructed conveyor chain.

The reduced friction results in increased smoothness of operation, which ensures that any irregular movement of the conveyor caused by skidding, or stick-slipping is completely eliminated right down to chain speeds as low as 0.5m/min.

Bearing roller conveyor chain has cured "stick-slip" and kinking problems on conveyors used in the assembly of large electric generators.

In an application on a bulk paper roller conveyor, the product has realised huge reductions in space requirements and a 40 to 50% decrease in total equipment costs.

BRCC has also overcome poor roller rotation on a pipe conveying line.

In the same application the product has reduced guide rail wear, vibration and noise.

Moving objects has never been easier since the advent of free flow conveyor chain.

Now a new design, known as Double Plus, takes the development a step further by allying conveying speeds twice that of normal free flow chain with reduced power consumption and noise.

The unique design of Double Plus chain means that chain speeds up to 60% slower can be used without affecting the object conveying speed.

Consequently, motor drive speeds can be reduced leading to substantial power savings, and to reduced noise levels, some 15dB lower than those of plastic side roller chains.

Double Plus' unique design incorporates a large centre roller, and a smaller outer roller which supports the chain on a guide rail.

When engaged, the large centre rollers (on which conveyed objects travel) rotate at the same rpm as the small rollers.

However, since the diameter of the large rollers is approximately 2.5 times that of the smaller ones, conveyed objects move along approximately 2.5 times faster than the chain.

Continuing developments in plastics mean that the material is playing an increasingly important role in the development of chains to meet modern manufacturing needs.

The lubricating properties of some plastics (Acetals especially) can provide a solution where the chain is difficult to get at or cannot be lubricated anyway.

Replacing lubrication oils, the same self-lube properties can also reduce troublesome maintenance tasks.

Finally, the metal upon metal contact which causes wear elongation is avoided if self-lubricating plastic sleeves are used.

The provision of self-lubricating polyacetal sleeves between chain pin and bush enables Tsubaki's Plastic Sleeve chain to achieve reduced running resistance and energy savings of up to 30%.

Other benefits are noise reductions of between 7-10dB and a 15% weight saving when compared with standard stainless-steel chain.

With oversize plastic rollers even greater weight savings, of up to 40%, can be realised.

Plastic Sleeve chain also provides benefits in terms of chain elongation.

Normally, chain wear, as measured by elongation, tends to accelerate after a certain period in chain made exclusively from steel.

However, any elongation in Plastic Sleeve chain is slight and incremental, due to the increased overall elasticity of the chain and the minimisation of metal-on-metal contact during operation.

No article looking at developments in chain technology could conclude without mentioning the workhorse of industry: steel roller chain.

Sophisticated computerised production techniques have enabled perfect concentricity and cylindrical accuracy to be achieved on Tsubaki's RS roller chain.

The pin surfaces are carburised using an advanced heat-treating process and the link plates and rollers are shot peened.

The surface areas between pins and bushings and between bushings and rollers are prelubricated and then the chains are preloaded continuously and accurately on multi-sprockets after assembly.

The result is a great improvement in performance: initial stretch is reduced to 0.01% and wear life is increased by 140% in comparison with competitive roller chains.

Also, as an insurance against dangerous ultimate strength failure, RS roller chain has a 20% greater tensile strength and impact resistance than demanded by ANSI standards.

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