JP2927586B

The invention is directed to a portable handheld tool such as a brushcutter which includes a work tool assembly and a drive motor connected by a drive shaft. The drive shaft is surrounded by a protective tube and is centrally held therein by means of a bearing sleeve unit. The bearing sleeve unit braces itself against the inner peripheral wall surface of the protective tube via outwardly extending support ribs. The bearing sleeve unit defines a bearing bore for holding and guiding the drive shaft within the protective tube. The bearing bore and the drive shaft conjointly define an annular bearing play gap therebetween whereby frictional heat generated in the bearing sleeve unit is reduced while vibrations of the drive shaft are developed and imparted to the bearing sleeve unit. The support ribs are configured so as to be resilient in the radial direction to attenuate the vibrations imparted to the bearing sleeve unit. A plurality of impact ribs extends substantially radially from the outer surface of the center portion for impacting against the inner wall surface in response to the vibrations thereby limiting the amplitude thereof.