A jack is a special device by which a heavy load is lifted and fixed at the required height. This mechanism is simply indispensable when performing any repair of the car, for example, when changing wheels.
Rolling hydraulic jack.
The most convenient and effective for work are hydraulic jacks, the working force of which is achieved with the help of hydraulic oil and piston. The assembly and repair of such a device can be done by hand.
Rolling Jack: principle of operation
The rolling jack belongs to the category of hydraulic, only has a slightly different design. On its body, made of metal, two pairs of wheels are mounted. In the holes on it are mounted a mechanism for lifting and a hydraulic cylinder, which, when extending in the horizontal direction, lifts the platform. The device itself gradually raises the car to the desired height, while it rolls under him.
The jack is moved by swinging the lever, and lowered by turning the valve screw. During the process of lowering the load, a tubular handle is placed on the valve screw, and then the partition enters its groove. When the handle is rotated around its axis, the screw itself rotates accordingly. When this happens, the pressure in the working cylinder is released, and the load is lowered to the desired height.
In order for the jack to serve for a long time, it is necessary to monitor the presence of oil in it and the condition of the gland and valves.
There are sliding hydraulic jacks used for personal purposes for cars with a weight category up to 3000 kg. Most often, such a device, equipped with pedals, necessary for pre-lifting, is used in automotive services and tire fitting stations. It can lift loads up to 4000 kg, quickly enough doing the work.
The jacks, which lift the load up to 20 tons and are equipped with pre-lift pedals, as well as a sliding crosshead, are designed to serve heavy machines and special vehicles. This mechanism has its drawbacks, which include the volumetric size and heavy weight, because of which it is difficult to move in the car. It requires a flat horizontal surface, such as asphalt or concrete.Back to table of contents
Repair of the rolling jack
It will take:
- capacity to drain the oil;
During the operation of the jack can break it. Failures of this device may include oil leakage, jamming when rising to a height, or, conversely, its refusal to sink. In any case, it should be repaired.
If the cause of failure is the flow of oil, then first you need to disassemble the device. Then pistons are removed from it and checked for corrosion. After that, all the dirt and the resulting corrosion is carefully removed. Further the stock is checked. In the event that it is bent and deformed, repair of the jack can be considered inappropriate.
The principle of operation of the hydraulic rolling jack.
Carrying out repair of the valve, which allows oil to pass through, it is necessary to unscrew it and check whether the dirt has got inside and whether its deformation has occurred. In the event that it has undergone mechanical deformation, the valve should be replaced. If it is contaminated, then the working fluid will flow due to the fact that the ball has stopped tightly into the saddle. Therefore, first, an old working fluid (oil) is drained into the prepared container, while pumping the system with a lever, raising and lowering it.
Then all parts are thoroughly washed from the dirt that has fallen, as well as from the remnants of old oil. At the same time, the replacement of all cuffs and sealing gaskets is obligatory. If the dirt got directly into the working cavity, then to remove it you will need to unscrew the casing head.
After that, kerosene is poured into its base, and the jack is pumped. In this case, the locking needle must be unscrewed. At the end, the kerosene is removed, and a clean working fluid is poured into the working cavity.
The performance of the jack can be reduced due to the accumulation of air bubbles in its working cavity, which get there due to lack of oil.
Repair in this case is as follows. First you need to open the plug at the oil tank and the relief valve. Then, at a rapid pace, the pump of a hydraulic press is pumped several times so that the air from the working cavity moves into the tank in which the oil is located. After that, the oil reservoir opening and the bypass valve are closed. If the whole process is done correctly, the jack will start working as usual. With the rest of the air in it, all actions are repeated again.
If this device does not work or lifts the load very slowly, then you can remove the air from the working cavity in another way. To do this, the locking needle turns one and a half or two turns. Then with the help of the hand behind the screw the plunger rises, reaching the extreme upper point.
After that it goes down to the bottom position. All actions are repeated two or three times. To avoid this problem in the future, you should periodically check the oil level in the jack and, if necessary, add working fluid to it.