Liquid sealed vibration isolating device

A liquid sealed vibration isolating device comprising:

• a first mounting member to be mounted on a side of a vibration source,
• a second mounting member to be mounted on a side to be vibrated,
• an insulator being placed between said first and second mounting members so as to absorb vibration,
• a liquid chamber using said insulator as a part of a wall thereof and being filled with a hydraulic liquid,
• a partition member for partitioning said liquid chamber into a primary liquid chamber and a secondary liquid chamber, said partition member including an opening and closing orifice passage provided between said primary liquid chamber and said secondary liquid chamber, and
• a valve portion being provided on a diaphragm enclosing said secondary liquid chamber and moveable between an open position and a closed position to open and close a port of said opening and closing orifice passage, wherein said valve portion is a thick rigid annular portion that is contacted with and separated from a valve seat portion provided around said port of said opening and closing orifice passage and comprises said thick annular wall portion integrally formed on the central area of the diaphragm to project upwardly and downwardly and a central movable elastic diaphragm portion that is provided on an inside of said annular thick wall portion, is thinner than said annular thick wall portion to be elastically deformable by a liquid pressure of the hydraulic liquid, and is elastically deformable in both the open position and closed position of said valve portion,
• said central movable elastic diaphragm portion being formed with a concave wall curved downwardly relative to said primary liquid chamber so that said central movable elastic diaphragm portion is concaved in an outward direction of said primary liquid chamber,
• wherein said central movable elastic diaphragm portion is as thick as an average thickness of a flexibly deformable portion around said annular thick wall portion of said diaphragm,
• wherein said diaphragm is provided with a crank-shaped portion outside of said annular thick wall portion, said crank-shaped portion having a horizontal portion and a vertically extending cylindrical portion, said horizontal portion being substantially aligned with the central moveable elastic diaphragm portion and extending outwardly in a radial direction from an outer periphery of an intermediate portion of said upwardly and downwardly projecting annular thick wall portion, said vertically extending cylindrical portion being bent generally at right angles from a tip of said horizontal portion to extend substantially vertically along the outer periphery of said annular thick wall portion,
• wherein a lower portion of said annular thick wall portion, which is disposed vertically below the intermediate portion of the annular thick wall portion from which the horizontal portion of the crank-shaped portion extends, defines a first cylinder;
• wherein said vertically extending cylindrical portion defines a second cylinder that is generally parallel to, and radially surrounds, the first cylinder, whereby said first and second cylinders form a double cylindrical portion;
• wherein an axis of the vertically extending cylindrical portion extends in an upward and downward direction, said vertically extending cylindrical portion being longer than the annular thick wall portion, said vertically extending cylindrical portion extending in the same direction as the vibration input direction,
• wherein the outer peripheral portion of said vertical portion is integrally formed with a ring-shaped metal fitting through a mutable structure portion bent in a wave form, and,
• wherein said crank-shaped portion is configured to increase rigidity of the vertically extending cylindrical portion with respect to vibration inputted to said valve portion in a vertical direction.