Working principle: Jack is divided into two kinds of mechanical jack and hydraulic jack, the focus is different.
The hydraulic jack is based on the principle of PASCAL's principle, that is: the pressure of the liquid everywhere is consistent, so that, in a balanced system, the pressure exerted on the small piston is relatively small, and the pressure exerted on the large piston is relatively large, so that it can keep the liquid static. So by transferring the liquid, you get different pressures at different ends, and you get a transformation. The hydraulic jack saw seen the use of this principle to achieve force transmission.
Mechanical jack adopts mechanical principle, in the past repeatedly pulled the handle, and pulled the claw to promote the ratchet clearance rotation, small bevel gear drives the bevel gear so that the lifting screw rotation so that the lifting sleeve gets up or down, and achieves the lifting pull function. But not as easy as a hydraulic jack.
1. Rack jack:by manpower through the lever and gear drive rack lift object. The lifting weight is generally not more than 20 tons, which can be used to support heavy objects for a long time. It is mainly used in places where the working conditions are inconvenient or where the lower claw needs to be used to lift heavy objects, such as railway rail operations.
2. Screw jack: by manpower through the screw pair drive, screw, or nut sleeve as the top lift. Ordinary screw jacks rely on thread self-locking function to support heavy objects, a simple structure, but low transmission efficiency, and slow return. The thread of the self-descending screw jack has no self-locking function, but it is equipped with a brake. Relax the brake, and the weight can quickly drop by itself, shortening the return time, but this kind of jack structure is more complex. Screw jack can support heavy objects for a long time, the maximum lifting weight has reached 100 tons, widely used. The lower part of the horizontal screw, but also make the weight do a small distance transverse.
3.Hydraulic jack: by the human or electric drive hydraulic pump, through the hydraulic system transmission, with the cylinder or piston as the top lift. Hydraulic jacks can be divided into integral types and separated types. Integrated pump and hydraulic cylinder into one; The separate pump is separated from the hydraulic cylinder and connected with a high-pressure hose in the middle. The hydraulic jack structure is compact, can smoothly lift heavy objects, has a maximum lifting weight of 1000 tons, a stroke of 1 meter, and high transmission efficiency, so it is widely used; however, it is easy to leak oil and should not support heavy objects for a long time. Such as long-term support need to choose a self-locking jack, screw jack, or hydraulic jack to reduce the height of the shape further or increase the lifting distance, which can be made into a multistage telescopic type. Hydraulic jacks in addition to the above basic type, according to the same principle can be modified into sliding template jacks, hydraulic lifting platforms, tension machines, etc., used in various special construction occasions.
