The screw jack, also known as the screw transmission system, is crucial for converting rotary motion into linear motion at a constant speed, or vice versa, transforming linear motion into rotary motion. It includes systems like the screw press and hydraulic jacks that primarily transfer kinetic energy, as well as those like the ball screw on machine tool operating tables that primarily transfer motion, and also includes systems that adjust the relative positions of components, such as the screw transmission systems. Screw jacks are divided into drag friction systems and rolling friction systems.
The screw jack is a fundamental lifting component widely used across various industries. The principle of the screw jack: It is composed of a worm gear reducer and a screw, with the reduction mechanism being the worm transmission. The worm drives the worm gear to maintain the reduction. The worm gear is equivalent to the nut of the lifting screw and matches with it. The center of the worm gear features a threaded structure, identical to the nut of the lifting screw and compatible with it.
The lifting speed of screw jack is equivalent to the ratio of worm key-in speed to the transmission ratio of worm and worm gear, followed by multiplying it by the pitch of the lifting screw. Due to its construction, such screw jacks are generally lubricated with grease, while some series are lubricated with oil, which offers the advantages of longer lifespan and smoother operation compared to those lubricated with grease.
The temperature rise in the helical ball screw lifting machine can cause each component inside the worm gear housing to expand at different rates, resulting in discrepancies in fit and gaps in the mating surfaces. The lubricating oil or hydraulic fluid used in the reducer can also thin or spoil under high temperatures, leading to leaks or ineffective lubrication.
The helical screw lift is basically applicable to all areas of the mechanical equipment's offset transmission system. It is used in railway vehicles for lifting platforms, large and medium-sized flexible clamps, measuring range tools, robotic welding, etc.; in the construction industry for lifting and hoisting equipment, automatic opening and closing of large windows and doors, or shop closing equipment; in water conservancy projects and other industrial production entrance opening equipment, radar detection and solar power generation remote sensing technology equipment; lifting platforms and cranes for the automotive industry; and in aerospace, national defense security, and defense transmission.
Nowadays, most screw jack lifting machines come with various methods and approaches, commonly using a stepped design, and all of them are equipped with an automatic locking feature. This allows for a stronger adaptation to certain factors or low-frequency close-tolerance operations without any related braking systems.
