Bladder type oil tank

The utility model relates to a bag oil tank used in hydraulic system, aiming to overcome the disadvantages of switching type oil tank in current hydraulic system in order to reduced the system malfunctions and extend the service life of the oil. Referring to the attached figure in the abstract, the bag oil tank mainly comprises an oil connector(1), a bag(3) and a casing(5) covering the tank, wherein the bag(3) is used as a volume variable oil storage container, which material and structure is similar to the air charging bag in normal hydraulic accumulator but oil(2) not air is charged into the bag; the oil connector(1) and the bag(3) are produced into an integer, which is fixed on the casing through nuts; because of small stress, the casing(5) can be made of rigid plastic or sheet iron for protecting the bag from damaging by sharp objects; air(4) is filled into the space between the bag(3) and the casing(5); and the bag communicates with the atmosphere out of the casing through an air filter(7) mounted on a casing cover(8) in order to maintain the air pressure in the casing identically equal to the atmosphere pressure.