Hydraulic inertial vibration isolator

Abstract

A hydraulic inertial vibration isolator is connected between a vibrating body and an isolated body. The vibration isolator comprises a cylinder which includes two chambers and a piston therebetween. The chambers are connected by a tuning passage in which a solid tuning slug is slidably disposed. The chambers and the portion of the tuning passage not occupied by the tuning slug are filled with liquid. Bypass passages connecting the tuning passage to the chambers allow the liquid pressures in the chambers to equalize when the amplitude of the tuning slug's oscillatory motion is sufficiently large, thereby limiting the tuning slug's amplitude. Dashpots axially disposed adjacent to either end of the tuning slug act to damp excessive tuning slug motion and to bias the tuning slug toward the center of the tuning passage. In response to vibration of the isolated body to which the vibration isolator is attached, an electronic control system supplies an alternating current of appropriate amplitude and phase to one or more magnetic coils disposed adjacent to the tuning slug, thereby matching the isolation frequency of the vibrating body-vibration isolator-isolated body system with the vibration frequency and adding energy to the vibration isolator to compensate for damping losses. As a result, virtually no vibration is transferred from the vibrating body to the isolated body.