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Techdrives has released a range of heavy-duty screw jacks with rated forces from 5 to 350kN; new models of up to 700kN will come on-stream in 2010.

Fourteen variants in travelling nut and travelling screw designs offer a comprehensive range of speeds and loads together with many configuration options.

These screw jacks are produced by linear-motion specialist Servomech.

Screw jacks deliver medium to high forces at strokes that can be short (100mm) or very long (up to 6,000mm), subject to mounting configuration.

They usually give outputs at low linear speeds but 150mm/s speeds are possible.

The screw jacks are simple in concept and are based on worm gearbox technology.

They have a range of variables and can match individual customer needs.

Inputs can be free shaft or motorised to give output speeds from 1mm/s to 150mm/s.

Screw jacks are often combined in groups with mechanical connection by spacer couplings.

A typical screw-jack application is lifting stage scenery, lids or platforms where it is common to have four screw jacks arranged in a H or U formation with one motor and coupling connections.

It is equally possible to motorise each screw jack and run them electrically gearlocked.

Other examples of use are on container cranes for trimming, positioning radio telescopes, lifting silos and steelmaking.

Servomech can offer two different mechanical configurations.

Travelling nut designs have the screw in a fixed position while a bronze nut runs up and down it.

Travelling screw designs have the screw rising and falling as it passes through the body of the screw jack.

The choice between the two designs is made by the mounting dimensions available.

Normally acme threads are used but ballscrews can be specified for increased duty cycles and high efficiency.

Motors can be AC asynchronous, DC or servo for positioning.

Other options include mechanical safety, for example stroke limits and wear control of the travelling nut.

Techdrives’ website presents the full range of Servomech screw jacks with catalogue downloads and enquiry sheets, an essential first step to establishing the specification.

Product engineers are available to give technical support.

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