Hydraulic antivibration sleeve

A hydraulic antivibration sleeve comprising:

• a rigid inner strength member extending longitudinally along a central axis between two axial ends;
• an annular rigid outer strength member which surrounds the inner strength member;
• an elastomer body interconnecting the inner and outer strength members, said elastomer body comprising:
• a first thick elastomer wall adapted to support a permanent load of value lying in a certain operating domain and applied between the inner and outer strength members parallel to a main vibration direction perpendicular to said central axis, said first thick elastomer wall presenting a central portion secured to the inner strength member and a peripheral portion secured to the outer strength member, thereby defining part of a first liquid-filled working chamber;
• and
• a second thick elastomer wall having a peripheral portion secured to the outer strength member and defining a second liquid-filled working chamber;
• a liquid-filled compensation chamber defined by at least a first flexible elastomer wall that is easily deformable and thinner than said first and second thick elastomer walls;
• a first constricted passage putting said first working chamber into communication with the compensation chamber;
• and
• a second constricted passage putting the second working chamber into communication with one of the other two chambers, the first and second constricted passages being dimensioned to present respective first and second different resonant frequencies;
• wherein the second working chamber is diametrically opposite to the first working chamber about the central axis, the two working chambers being substantially in alignment along the main direction of vibration, the second thick elastomer wall presenting a free central portion which is disposed in the vicinity of the inner strength member and which is independent of said inner strength member;
• and
• wherein the elastomer body is so dimensioned:
• that the free central portion of the second elastomer wall is in contact with the inner strength member when said permanent load lies in a first range of values belonging to said operating domain;
• and
• that the free central portion of the second elastomer wall is separate from the inner strength member by an empty space when the permanent load lies in a second range of values complementary to the first range of values in said operating domain.