Screw Jack

Screw Jack

Common all over the world, screw jacks are vital tools wherever there is a need to hold, lift, align, and position a load. Their high synchronization and reliability make them suitable for a broad range of uses where alternative handling methods cannot achieve tangible results. These range of applications are spread across industrial sectors that include steel works, laboratory and medical, aerospace, mechanical, nuclear, pharmaceutical, water processing, and packaging equipment.

Different threads are used in screw-jack based systems. In heavy-duty uses, a buttress or square thread is used due to its low wear and friction level. An acme thread is used for technical purposes despite the high friction. This is because it allows for smoother engagement, it's easy to manufacture, stronger than a sizeable thread, and it's possible to compensate for wear. To make the threads more durable, the ball screw uses a re-circulation ball that reduces friction.

The main components include a worm screw, gear housing, and a trapezoidal lifting screw. The rotation of a worm gear screw jack and thread size determines lifting the screw’s linear motion speed as the screw moves through the turning gears. The lifting screw does not oscillate in some models but moves around its axis. To reduce friction, the lifting nut that moves along the bolt is made of bronze. Depending on the motion type, the screw jack can be used as linear motors, lifts, and actuators.

There are various types of screw jacks based on the specific program. The variations can be achieved with a ball screw jack or machine screw jack, depending on the system design on which they are fitted.

• Translating screw jack: This has the worm wheel revolution acting directly on the lead-screw that in turn translates linearly.
• Rotating screw jack: This has the lead fixed to the worm wheel where the revolution of the worm wheel makes the lead screw revolve. This translates the nut along the lead screw when attached to the load.
• Translating keyed screw jack: This has the lead screw keyed to prevent revolution. This is beneficial where the end cannot be attached to the load.

The translation speed is affected by the number of lead-screw starts. A system with a single start screw is self-locking because of the greater friction angle of the threads compared to the lead angle. In this case, an axial force on the bolt cannot cause rotation. With the invention of a screw jack, the otherwise almost impossible and time-consuming tasks have become easier and more efficient.