US Patent 6988851 Concrete screed with vibration isolation

A vibratory concrete screed includes a vibration isolation system that minimizes the transmission of vibrations to the operator under normal operating conditions, but becomes more rigid during screed control forces applied to the blade through the isolation system when the operator applies greater forces to the operator handle. The system includes low durometer elastomer vibration isolators isolating the operator handle from the vibration exciter and screed blade in a manner that limits vertical compressive movement of the isolators, yet permits substantially greater horizontal shear movement to effectively isolate the operator from vibration. The isolator mounting arrangement also includes retainers that engage the isolator to limit the amplitude of horizontal shear movement when the operator applies a greater control force to the operator handle.