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What is a jack?

Updated: Dec 14, 2020

A jack is a device that can lift heavy objects. It is mainly a small and light lifting device that uses a rigid lifting member as a working device and pushes the heavy objects within a small stroke of the top bracket or the bottom claw. Jack has the purpose of lifting and supporting, so it is often used in transportation, mining, vehicle maintenance, and other industries. Its structure is sturdy and light compact, easy to carry and operate.

Types of Jack

Jacks can be divided into three different types, that is, hydraulic jacks, screw jacks, and electric jacks. Different types of jacks have different operating principles.

1. Hydraulic Jack

A hydraulic jack is a jack that uses a plunger or a hydraulic cylinder to apply pressure to lift the load and acts as a rigid jack. It mainly uses the pressure generated in the cylinder chamber to lift the specified load. The advantages of hydraulic jacks are compact structure, large supporting force, stable work, and self-locking function. General hydraulic jacks have an excellent supporting capacity, while heavy hydraulic jacks can support loads exceeding 100t.

The most basic principle based on the hydraulic transmission is Pascal's law, the pressure of the liquid is the same everywhere. In the balance system, we apply a smaller pressure on the smaller piston, which is equivalent to applying a larger pressure on the larger piston, so that the liquid can remain stationary. Therefore, by transferring liquid, different pressures can be obtained at different ends, and conversion can also be achieved. It is often regarded as the intermediate medium in the hydraulic transmission system, which plays the role of transmitting and converting energy. In addition, it also plays the role of lubrication, cooling, corrosion protection, and flushing of the components in the hydraulic system.

In the market, there are two types of the most commonly used hydraulic jacks which are bottle jack and floor jack.

The lifting capacity of the bottle jack is very wide, from more than 40 kilograms to several tons. The bottom of the bottle jack has a hydraulic cylinder. It uses a vertical shaft to support the bearing pad, and this bearing pad can support heavy objects.

The difference between a floor jack and a bottle jack is that the floor jack uses a horizontal shaft to operate. The device is mainly used in the automobile maintenance industry to lift the car from the ground. The handle of the floor jack is connected to its lifting pad, so when we push the handle, the heavy object can be lifted.

2. Screw Jack

The screw jack is driven by manpower through a screw pair, and the screw or nut sleeve is used as the lifting part. Ordinary screw jacks have a self-locking function to support heavy objects by the thread. Its structure is generally simple, but its transmission efficiency is low. The other is a self-falling screw jack. Its thread has no self-locking function, but it is equipped with a brake. By releasing the brake, the heavy objects can descend quickly by themselves, and the return time can also be shortened. However, the structure of this jack is more complicated.

The mechanical principle of the screw jack is that by reciprocating the handle, pulling the pawl will push the ratchet gap to rotate, the small bevel gear will drive the big bevel gear to rotate together, and the lifting screw will also rotate so that the lifting sleeve can be raised or lowered, and to achieve the function of lifting force.

Screw jacks can support heavy objects for a long time, up to 100 tons. It is often used as a support for construction projects, railway vehicle maintenance, mines, and general heavy objects lifting and lowering.

Several advantages of screw jack are listed below:

  1. Lightweight and easy to carry

  2. Simple structure

  3. The importance of lifting

  4. Easy maintenance

  5. Safe and reliable when used

3. Electric Jack

The electric jack is a combination of a hydraulic cylinder and an electric pumping station. It is equipped with a pressure holding device inside to prevent overpressure. If an overpressure occurs, the jack will not return to a certain position. The special structure can double the protection of the jack. After the lowering item is equipped with a dive device, the purpose of low height and high stroke can be achieved. It can also be used in various operations such as jacking, pushing, pulling, and squeezing.

Electric jacks are widely used in heavy lifting, power maintenance, bridge and ship repair, road and railway construction, equipment disassembly, and so on.


The following points are the things you need to pay attention to when using jacks:

  1. When we use the jack, we need to place the jack on a hard and stable floor to prevent the jack from tilting after being stressed. If you are on a smooth or soft bottom surface, you can put a hard wooden board under the jack to prevent sliding after touching the surface.

  2. Choose different jacks according to different loads, because jacks cannot be overloaded.

  3. When using the jack, it needs to rise and fall slowly to ensure workplace safety.

  4. The jack also needs careful maintenance, and the oil pressure should be checked regularly.

Through the above article, we explained the types of jacks and their uses. Hope this article can increase your understanding of jacks. If you have any questions or problems in choosing a jack, you can contact our customer service at 011-7000 7687 or email us at MecHero can choose a suitable jack for you.

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