Study on the vibration reduction of concrete breakers (2nd report, Vibration reduction due to the dynamic balancer driven by positive cam, and vibration isolation due to the elastic coupling between crank shaft and motor.

Abstract

In the previous paper, a survey was reported on the vibrations of electrical concrete breakers, one of the typical piston-operated vibrating tools. From various analyses of vibration measurements, it was confirmed that the main cause of vibration sensitivity was the reaction force of the connecting rod via the piston, resulting from rapid air compression rather than the impingement of the chisel for the chisel holder on the front of tool. Based on such a conclusion, two kinds of system were adapted on the vibration reduction and vibration isolation of the breakers. One of them consists of the dynamic balancer driven by the positive cam, and the other consists of the elastic coupling between the crank shaft incorporated in the cylinder body and the motor section. The former was not always effective in reducing vibration in handles because of the restricted size and weight, but the latter was considerably effective in isolating vibration in handles, about 6∼10 dB smaller in vibration level than conventional ones.