February 2011
Screw jacks lift 9 tonne maintenance cradle
Building skyline improved lifting system
In the heart of Paddington at the new Merchant Square commercial development, Servomech screw jacks are used to lower three maintenance cradles below the building skyline when they are not in use. Three complete lifting systems were supplied to façade access specialist CoxGomyl Integral of Sheffield. Each system includes four screw jacks together with the connecting couplings, gearboxes and the electric motor to drive them. When the 9 tonne building maintenance cradles are not in use, they are lowered 1.3m to become invisible from the surrounding area, thus preserving the clean lines of the building.
Each lifting system is an ‘H’ configuration driven from a 3.0kW geared brake motor at the centre. Universal joint spacer couplings and bevel gearboxes connect to the four screw jacks at the corners, each rated at 50 kN. A travelling screw design was chosen where actuation of the screw jack drives the screw through the body of the jack. In this case the screws are fixed to the framework so that the jack bodies run up and down them carrying the maintenance cradle. The screw jacks include the option of a safety nut which is a back-up to prevent the cradle dropping in the unlikely event of extreme wear or a catastrophic failure.
Servomech screw jacks are available in the UK through the Techdrives division of Lenze. Both travelling screw and travelling nut versions are available and the range runs from 5 to 350 kN force, speeds up to 150mm/s and strokes to 6m. Technical support is available including design of complete systems.
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