According to the structural characteristics, it can be divided into rack jack, screw jack and hydraulic jack.
① Rack jack: manpower drives the rack to lift heavy objects through levers and gears. The lifting capacity is generally less than 20 tons, and it can support heavy objects for a long time. It is mainly used in places with inconvenient working conditions or places where heavy objects need to be lifted by lower claws, such as railway rail lifting.
② Screw jack: it is driven by human power through screw pair, with screw or nut sleeve as the jacking piece. The common screw jack supports heavy objects by the self-locking function of threads, which has simple structure, but low transmission efficiency and slow return. The thread of the self-falling screw jack has no self-locking function and is equipped with a brake. When the brake is released, the heavy object can descend quickly and shorten the return time, but the structure of this jack is more complicated. Screw jack can support heavy objects for a long time, and its maximum lifting capacity reaches100t, so it is widely used. After the horizontal screw is installed at the lower part, the weight can move laterally for a short distance.
③ Hydraulic jack: the hydraulic pump is driven by manpower or electricity, driven by the hydraulic system, and the cylinder or piston is used as the jack. Hydraulic jacks can be divided into integral type and separated type. The integral pump and the hydraulic cylinder are connected into a whole; The separation pump is separated from the hydraulic cylinder and connected with a high-pressure hose in the middle. Hydraulic jack is compact in structure, can lift heavy objects smoothly, with the maximum lifting capacity of 750 tons and high transmission efficiency, so it is widely used. But it is easy to leak oil and is not suitable for supporting heavy objects for a long time.
Screw jack and hydraulic jack can be made into multi-stage telescopic type to further reduce the overall height or increase the lifting distance.
In addition to the above basic types, hydraulic jacks can also be modified into sliding mode jacks, hydraulic lifting tables, tensioners, etc. According to the same principle, it is used in various special construction occasions. By structure
According to other ways, it can be divided into separate jack, horizontal jack, claw jack, synchronous jack, hydraulic jack, electric jack and so on!
In addition to the above basic types, hydraulic jacks can also be modified into sliding mode jacks, hydraulic lifting tables, tensioners, etc. According to the same principle, it is used in various special construction occasions.
Working principle of jack.
There are mechanical jacks and hydraulic jacks with different principles. In principle, the most basic principle of hydraulic transmission is Pascal's principle, that is to say, the pressure of liquid is the same everywhere, so that in a balanced system, the pressure acting on the smaller piston is relatively small, while the pressure acting on the larger piston is relatively large, which can keep the liquid still. Therefore, through the transfer of liquid, different pressures at different ends can be obtained, thus achieving the purpose of conversion. The hydraulic jack we often see uses this principle to realize force transmission. According to the mechanical principle of screw jack, by pulling the handle back and forth, the claw pushes the ratchet wheel to rotate, and the small bevel gear drives the large bevel gear to rotate the weight-lifting screw, so that the lifting sleeve rises or falls, thus achieving the effect of lifting the pulling force. But not as simple as a hydraulic jack.
Second, the measuring tool-jack
According to JB 34 1 1.58-99 standard, it is used to support parts during testing. The products are steel parts and cast iron parts respectively, and the outer surface is chrome-plated and painted.
Specification (mm) adjustable height (mm) single load (kg)
φ35×60 60 35
φ50×80 80 50
φ70× 100 100 70
φ 100× 150 150 100
φ 150×250 250 150
φ200×300 300 200
φ260×400 400 260
φ280×450 450 280
φ300×500 500 300 jack
The top of the transformers
Autobot, a scholar, hates war, but he knows that he will die if he doesn't fight, so he fights with Optimus Prime. He used wisdom more than force. Jack is a cautious and calm person. His inventions are varied, but he can always help autobots. He once saved the Autobots and stayed with them in Skyfire, Sebert. For the safety of his companions, he once imprisoned himself under the clutches of the Dragon King.