Screw jacks for medium and high force linear motion
New range of industrial screw jacks
September 2009
Available from this website is a new range of heavy duty screw jacks with rated forces from 5kN to 350kN plus new models up to 700kN coming 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 who have 20 years design and manufacturing experience.
Screw jacks are used to deliver medium to high forces at strokes that can be short, 100mm, or very long up to 6000mm subject to mounting configuration. They usually give outputs at low linear speeds but up to 150mm/s is possible. Although simple in concept based on worm gearbox technology, screw jacks have a wide range of variables and should be considered as engineered products to match individual customer needs. Inputs can be free shaft or motorised to give output speeds from 1 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 4 screw jacks arranged in a H or U formation with one motor and coupling connections. It would equally be 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 offer two different mechanical configurations. Travelling nut designs have the screw in a fixed position whilst 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.
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