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    How does Hydraulic Jack Work?

    A hydraulic jack is kind of the simplest lifting equipment whose lifting height is little (less than 1m). The hydraulic jack has a compact structure, stable operation, and self-locking effect, so it is widely used. Jacks are mainly used in factories, mines, transportation, and other fields as vehicle repairs and other lifting, support, and other work. Its structure is light and strong, flexible and reliable, and can be carried and operated by one person. As a tool with a wide range of uses, the hydraulic jack can only play its role better if you understand its principle. Next, let's learn how the hydraulic jack works and how to use it.

    Lifting process

    Pump suction process

    When the lever handle is lifted by hand, the small piston is driven upward, and the sealed working volume in the pump body 2 increases. At this time, since the oil discharge check valve 3 and the oil discharge valve 8 respectively close their respective oil passages, the working volume in the pump body 2 increases to form a partial vacuum. Under the action of atmospheric pressure, the oil in the oil tank opens the oil suction check valve 4 and flows into pump body 2 through the oil pipe to complete an oil suction action.

    Pumping oil and heavy lifting process10 ton hydraulic bottle jack

    When the lever handle 1 is pressed down, the small piston is driven to move down, the working volume of the small oil chamber in the oil grease pump body 2 is reduced, and the oil in it is squeezed out, then the oil discharge check valve 3 is pushed open (at this time, the oil suction check valve 3 valve 4 automatically closes the oil path leading to the oil tank). And the oil enters the hydraulic cylinder (oil chamber) 11 through the oil pipe. Since the hydraulic cylinder (oil chamber) 11 is also a sealed working volume, the force generated by the squeezed oil will push the large piston up and lift the weight to do the work. Repeatedly lifting and pressing the lever handle can make the heavy object continuously rise to achieve the purpose of lifting.

    Heavy object falling process

    When the big piston returns downwards, open the oil drain valve 8 (rotate 90°), then the oil in the hydraulic cylinder (oil chamber) 11 will flow back to the oil tank 5 under the action of the weight, and the big piston will drop to its original position.

    Through the working process of the hydraulic jack, we can conclude that the working principle of hydraulic transmission is: using oil as the working medium, the movement is transmitted through the change of the sealed volume, and the power is transmitted through the internal pressure of the oil. Hydraulic transmission is essentially an energy conversion device.

    Working principle

    The principle of the hydraulic jack is Pascal's principle (the basic equation of static pressure p=p0+ρgh), that is to say, the pressure of the liquid is the same everywhere, so that in a balanced system, the pressure exerted on the smaller piston is relatively small, and the pressure exerted on the large piston is relatively high, which can keep the liquid still. Therefore, through the transmission of liquid, different pressures on different ends can be obtained, so that a transformation can be achieved. Generally, a hydraulic jack is exactly to have utilized this principle to reach the transmission of power.

    In simple terms, the working process is to compress the hydraulic medium (usually oil) by the hydraulic cylinder to form a certain pressure to exert its kinetic energy, which is used to compress and stretch the object, so that the object can be lifted, landed, and stamped.

    Hydraulic jack working principle

    First of all, the hydraulic jack needs two cylinders, one is called the piston cylinder, which has a piston; the other is called a fixed cylinder. The piston cylinder is installed at the head of the hydraulic cylinder, and the fixed cylinder is installed at the tail of the hydraulic cylinder, which is connected to each other through the piston cylinders to form a complete hydraulic cylinder structure.

    Next, the hydraulic oil will be pressed into the hydraulic cylinder, which will cause the piston to move in the direction of the head and tail to generate pressure. During the piston stroke, the hydraulic oil is squeezed out and flows into the container from the tail of the piston, thereby realizing the lifting and lowering of the jack. Eventually, the hydraulic oil returns to the head of the hydraulic cylinder, pushing the piston to continue working, closing the hydraulic power system.

    In summary, the hydraulic jack forms pressure through liquid compression, which makes the piston cylinder generate a kind of kinetic energy to lift and punch objects. The entire hydraulic system continuously iterates to form a driving force, realizes the effective manipulation of objects, and provides effective means for the production and care of enterprises.


    All parts must be checked before use. Mainly check whether there is oil leakage in pistons, joints, high-pressure hoses, etc. When using, strictly abide by the regulations in the main parameters, and avoid super height and overloading. Otherwise, when the lifting height or lifting tonnage exceeds the regulations, serious oil leakage will occur on the top of the hydraulic cylinder.

    If the amount of oil in the manual hydraulic pump is insufficient, it is necessary to add fully filtered hydraulic oil to the pump before it can work. The selection of the center of gravity of the heavy object should be moderate, the force point of the jack should be reasonably selected, and the bottom surface should be flat. At the same time, the soft and hard conditions of the ground should be considered, whether it should be lined with tough wood, and whether the placement is stable, so as to avoid sinking or tilting under the load.

    After the jack lifts the heavy object, the support materials should be used to support the heavy object firmly in time. If several jacks are required to lift at the same time, in addition to placing the jacks correctly, attention should also be paid to the load of each jack should be balanced. Pay attention to keeping the lifting speed synchronous to prevent the danger caused by the tilt of the lifted heavy object.

    When using the jack, first place the hydraulic cylinder, and then tighten the oil drain screw on the hydraulic pump to work. To lower the piston rod, slightly loosen the handwheel of the manual hydraulic pump in the counterclockwise direction, the hydraulic cylinder is unloaded, and the piston rod gradually descends. Otherwise, falling too fast will be dangerous.

    The detachable jack adopts a spring return structure. After lifting, it can be taken out quickly, but the connected hose cannot be used to pull the jack. Because the lifting stroke of the jack is small, the rated stroke should not be exceeded during use, so as not to damage the jack. Avoid severe vibration of the jack during use (such as hitting the workpiece with a hammer when the jack is loaded).

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