Liquid sealed vibration isolating device

A liquid sealed vibration isolating device comprising a first mounting means being mounted on the vibration source side, a second mounting means being mounted on the vibration transmission side, an elastic main body being provided between the first and second mounting members, a liquid chamber forming a portion of its wall with the elastic main body, a partition member for partitioning the liquid chamber into a primary liquid chamber and a secondary liquid chamber, a damping orifice communicating between the primary liquid chamber and the secondary liquid chamber and producing a first resonance by a predetermined low frequency vibration, a movable diaphragm being provided on at least a portion of the partition member and elastically deformable to absorb a change in internal pressure of the primary liquid chamber, and a leg portion integrally projecting from an outer circumferential portion on the secondary liquid chamber side of the movable diaphragm and being pressed against a pressed portion formed on a portion of a frame member which is provided for fixing a circumference of the partition member, wherein a third liquid chamber is provided between the leg portion and the frame member, and an openable and closable orifice clearance that communicates with the third liquid chamber, is formed between the leg portion and the pressed portion, wherein the orifice clearance is closed when the leg portion comes in contact with the pressed portion, to close up the third liquid chamber tightly, while it is opened when the leg portion is brought out of contact with the pressed portion, to open the third liquid chamber, and wherein a second resonance which resonates at a different frequency from the first resonance produced by the damping orifice is created in the orifice clearance due to the flow of a hydraulic fluid by the opening and closing of the third liquid chamber.