A screw jack is a gearbox assembly (either worm gear or bevel gear) and a transmission product (lead screw, ball screw or roller screw) which through use of a motor is used to convert rotary into linear motion. They can be used to push, pull, tension, lock, unlock, tilt, pivot, roll, slide and lift or lower loads, anything from a few kilos to thousands of tonnes.

screw jack motion

Screw jacks are essential components in automated machinery. Safety and legislative concerns drive the automation of handling and lifting of heavy loads, particularly in regions which have developed workplace and health and safety legislation.

The trend to electromechanical actuation from hydraulic actuation.

Screw jacks usually operate in high-load applications. The competing technology at high loads tends to be hydraulics; however, hydraulics are less energy-efficient than electro-mechanical actuation provided by screw jacks. Hydraulic systems waste energy as the fluid circulates at constant pressure, regardless of the amount of work required to be carried out by hydraulic positioning. A hydraulic jack or ram requires a constant pressure to maintain its position when holding a load in place. By contrast, an electric motor used to power a screw jack uses energy only when it drives the load to a required position.

The advantages of electro-mechanical over hydraulic can be summarized by:

  • Demand for increased safety, in the event of power loss, screw jacks can be self locking
  • Demand for machinery that operates with better energy efficiency
  • Demand for machinery that operates greater levels of precision
  • Machinery that requires less maintenance
  • Machinery that requires less manual intervention to set up processes
  • Increased range of actuation in terms of variable positioning
  • Accurate and smooth delivery of force
  • Cleaner machinery
example screw jack applications