Vibration isolating apparatus

Claim 1

A vibration isolating apparatus interposed between a vibration generating portion and a vibration receiving portion so as to absorb vibrations from said vibration generating portion, comprising: (a) a base plate secured to said vibration receiving portion; (b) a resilient member supported on said base plate to define a hollow chamber between said resilient member and said base plate; (c) a top plate secured to said resilient member to be applied for mounting said vibration generating portion thereon; (d) a diaphragm disposed in the hollow chamber to define a liquid chamber between said diaphragm and said resilient member; (e) a partition plate disposed in said liquid chamber to divide said liquid chamber into two small liquid chambers; (f) a large orifice formed on said partition plate to provide communication between said small liquid chambers; (g) a small orifice provided on said partition plate around said large orifice for providing communication between said small liquid chambers, the opening area of the small orifice being smaller than that of said large orifice; (h) a valve body disposed in the liquid chamber, for opening and closing said large orifice; and (i) a cylinder fixed to said base plate and having a driving shaft fixed to said valve body through said diaphragm, said cylinder driving said driving shaft to open said large orifice when a vibration equal to or greater than a predetermined frequency is generated from said vibration generating portion; whereby vibrations below said predetermined frequency are absorbed by means of a viscous resistance caused by liquid flowing through said small orifice between said small liquid chambers; and further whereby vibrations equal to or greater than said predetermined frequency are absorbed by means of liquid-mass resonance caused by liquid flowing through said large orifice between said small liquid chambers.