What Is a Jack Screw ?
A jack screw is a screw-type jack that utilizes a screw screw.
A jack is a mechanism that can raise and lower heavy objects with little force, and the principle of the screw is used for the raising and lowering motion. Other types of jacks besides jack screws include hydraulic and other types of jacks.
In addition to lifting and lowering heavy objects, jack screws can also be used for moving, rotating, and positioning heavy objects. The jack screws are generally driven manually or by a motor, and are used for inspection and repair of vehicles and ships, as well as on construction sites and in factories.
They may also be used in place of hydraulic presses because of their extremely high output relative to input.
Uses of Jack Screws
Jack screws are used in steel material manufacturing sites, metal processing equipment, automotive parts manufacturing equipment, liquid crystal display and semiconductor washing machines, and substrate conveyors. Screw jacks are incorporated into large equipment, etc., from the equipment design stage.
Our familiar example is a large lift for vehicle inspection in an automobile repair shop. At construction sites, jack screws are sometimes used for height adjustment during the temporary assembly process before welding steel materials.
Principle of Jack Screws
The principle of the jack screw is based on the principle of the screw. Screws are used to convert rotational motion into linear motion for lifting and lowering. A reduction gear with a worm gear is used to drive the jack screw.
The worm refers to the input shaft, and the worm shaft has a spiral-shaped gear. A worm wheel is mounted on the output side to receive the rotation of the worm, and the worm wheel rotates in accordance with the rotation of the worm.
In this image, the worm is the male thread and the worm wheel is the female thread. When the male screw is turned, the screw is tightened with more force than the force of the male screw. The worm reduction gear converts this strong tightening force directly into high-torque rotational force.
Types of Jack Screws
There are two main types of jack screws, depending on the shape of the screw. There are two main types of screw jacks depending on the screw shape: trapezoidal screw type and ball screw type.
Just as a jack screw that has been tightened cannot be pulled out even if it is pulled as it is, a jack screw will not easily fall apart even if a load is applied to it. However, the stability of holding the position under load differs between the trapezoidal screw type and the ball screw type.
1. Trapezoidal Screw Type
The trapezoidal screw type has a self-locking function, so there is no need to worry about reversal (loosening of the jack) no matter where the screw is stopped. Trapezoidal jack screws do not require a separate brake mechanism.
2. Ball Screw Type
Ball screw jacks do not have a self-locking function and require a separate brake (e.g., a magnetic brake). However, the ball screw type can be raised and lowered more efficiently than the trapezoidal screw type, resulting in higher work efficiency and lower power costs.
How to Select a Jack Screw
Jack screws are both versatile and functional, and can be used in a wide variety of ways, depending on your ideas. However, care must be taken when selecting a jack screw for use as part of a large piece of equipment. In particular, if jack screws are not selected based on accurate design regarding “input,” they may be damaged.
Other Information on Jack Screws
Bevel Jacks
Jack screws use worm gears to convert rotational motion to lifting and lowering motion, but there are also bevel jacks that use bevel gears. Bevel gears are also called bevel gears, and have a shape of a cone with gears engraved on it.
In general, the difference between worm gears and bevel gears is the reduction ratio obtained and the transmission efficiency of the gears. The gear ratio of bevel gears is about 1~10, while worm gears can reduce the speed up to 100. The advantage of a worm gear is that a large reduction ratio allows a large lifting force to be obtained even with a small motor.
However, the transmission efficiency of worm gears is lower than that of bevel gears. Note that if the reduction ratio is large and the transmission efficiency of the gears is low, a longer lifting and lowering time is required, and more power is needed to operate the motor in the same time.