A fluid filled cylindrical elastic mount interposed between two members of a vibration system, comprising:
- a center shaft member attached to one of said two members of said vibration system;
- an intermediate sleeve disposed radially outwardly of said center shaft member with a predetermined radial spacing therebetween and having a first window, a second window smaller than said first window and a third window smaller than said second window, said first, second and third windows being spaced apart from one another in a circumferential direction of said intermediate sleeve;
- an elastic body interposed between and elastically connecting said center shaft member and said intermediate sleeve, said elastic body having a first pocket, a second pocket and a third pocket which are open in an outer circumferential surface of said intermediate sleeve through said first, second and third windows of said intermediate sleeve, respectively, said first pocket being located in one of two diametrically opposed circumferential portions of said mount while said second and third pockets being located in the other circumferential portion;
- an outer sleeve member radially outwardly disposed on and fixed to said intermediate sleeve, and attached to the other member of said vibration system;
- a first flexible diaphragm closing said first pocket;
- said elastic body having an axial void which is formed through a portion of said elastic body between said center shaft member and said second and third pockets, over an entire axial length of said elastic body and in a circumferential direction of said elastic body with a circumferential length of about a half of a circumference of said elastic body, such that a major portion of said elastic body is located in said one circumferential portion of said mount and such that bottom wall portions of said second and third pockets respectively provide a second flexible diaphragm having a spring stiffness value smaller than that of said first flexible diaphragm, and a third flexible diaphragm having a spring stiffness value larger than that of said first flexible diaphragm;
- a generally cylindrical orifice member interposed between said intermediate sleeve and including a first circumferential portion which divides said first pocket into a radially inner pressure-receiving chamber partially defined by said elastic body and a radially outer first equilibrium chamber partially defined by said first flexible diaphragm, said orifice member further including a second circumferential portion closing said second pocket so as to provide a second equilibrium chamber partially defined by said second flexible diaphragm, and a third circumferential portion closing said third pocket so as to provide a third equilibrium chamber partially defined by said third flexible diaphragm, said orifice member cooperating with said outer sleeve member to define a first orifice passage for fluid communication between said pressure-receiving chamber and said first equilibrium chamber, a second orifice passage for a fluid communication between said pressure-receiving chamber and said second equilibrium and a third orifice passage for fluid communication between said pressure-receiving chamber and said third equilibrium chamber, a ratio of a cross sectional area to a circumferential length of said second orifice passage being lower than that of said first orifice passage, and a ratio of a cross sectional area to a circumferential length of said third orifice passage being higher than that of said first orifice passage;
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- a non-compressible fluid filling said pressure-receiving chamber and said first, second and third equilibrium chambers.