A motor driven eccentric vibrator with a spring isolated biasing mass for applying force to an earth penetrating device to cause the device to penetrate into the earth. The vibrator is rigidly attached to a housing which is rigidly attached to the earth penetrating element, which may be a sampling/core tube, while the biasing mass is suspended from the housing by a suspension that allows relative motion between the housing and the biasing mass in a vertical direction parallel to the longitudinal axis of the earth penetrating element. The biasing mass serves to apply a down force on the housing while not significantly reducing the amplitude of the vibrational displacement of the housing in a vertical direction. This mass also reduces the vibrational displacement of the housing in a horizontal direction caused by a single eccentric vibrator.
展开▼
