Screw Jack Working Principle
Screw Jacks are mechanical transmission devices used to convert rotational motion into linear motion for wide range of industrial applications. They incorporate a worm gearbox mechanism where an alloy steel worm rotates a high strength bronze worm gear. Rotation of worm gear causes a linear motion of lifting screw or traveling nut on the screw. Screw jacks enable linear motion solutions with precise positioning and smooth operation. They can be produced for load capacities between 5kN and 2000 kN. The linear motion speed and load capacity of lifting screw depends on the thread size, pitch and rotation ratio of worm gears.
Main components of screw jacks are; trapezoidal lifting screw, worm screw, worm gear and gear housing. Worm screw is rotated manually or by motor. With the rotation of the worm gear, the trapezoidal screw inside the screw jack moves linearly upwards or downwards. If the trapezoidal screw tip is connected to a free load, the trapezoidal screw rotates circularly due to friction between the screw threads . So to have a linear only motion, the rotation of load is to be prevented mechanically.
Travelling Nut / Rotating Screw
Main components of travelling ball nut screw jacks are; trapezoidal lifting screw, worm screw, worm gear, lifting nut and gear housing. Worm screw is rotated manually or by motor. The lifting lead screw is fixed to the worm gear therefore the rotation of the worm gear causes rotation of lead screw about it’s axis. So the trapezoidal lead screw does not move up and down. The inside threaded bronze nut on the lifting screw moves linearly upwards or downwards. In travelling nut – rotating screw type screw jacks the trapezoidal screw does not go beyond the jack base. Thus, unlike travelling ball screw jacks, the gear housing could be installed on a flat surface.
Mechanical Screw Jack
Mechanical lifting and pulling jacks are used in industrial plants, ships, machinery assembly for lifting , pushing and pulling heavy loads and assembling large structures. Also known as journal jacks, mechanical screw jacks are produced as an alternative to hydraulic screw jacks. They can be operated at any orientation without any risk of oil leakage. The light and rigid body of mechanical journal jacks make them easy to use manually at every condition.
Screw Jack Types
Plain Head Screw Jack
Plain head type screw jacks are used in multi purpose applications. For free loads, linear motion is provided by the keyed lead screw option which makes a linear motion without unintended self rotation. The auto blocking system prevents the load from self sliding back.
Screw Jack With Top Flange
Top flange plated screw jacks offer linear mechanical movement and ease of installation due to properly sized top connection flange. The design of flange enables both push and pull applications for wide range of machineries.
Clevis End Screw Jack
A clevis end connection allows for quick and easy connection of screw jack lifting screw to other system components. Clevis joints are used to support linear thrust or tractive movements for different kind of mechanical applications. They are perfect fit for precise angular motion control applications.
Travelling Nut Screw Jack
Travelling ball nut screw jacks have a fixed length lead screw that rotates around it’s own axis. Load is attached to the traveling nut that translates linearly along the rotating screw. This type of jack is ideal for applications that require a flush mount on planar surfaces.
Screw Jack Types
Screw Jack Assembly Examples
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