Abstract: A tool-bit holding device in a percussion tool includes a rotatable and axially-movable retainer sleeve for accommodating a shank of a tool bit. A lock member supported by the retainer sleeve is movable radially with respect to the retainer sleeve. The lock member can engage the shank of the tool bit to limit axial movement of the tool bit. A small-diameter surface portion formed by an inner surface of a fixed front cover contacts the rock member and projects at least part of the lock member inward of the retainer sleeve to engage the lock member with the shank of the tool bit when the retainer sleeve is placed at an active position. A conic surface portion formed by the inner surface of the front cover is engageable with the lock member, and is able to variably limit radial movement of the lock member as the retainer sleeve moves axially.

Abstract: A tool-bit holding device in a percussion tool includes a rotatable and axially-movable retainer sleeve for accommodating a shank of a tool bit. A lock member supported by the retainer sleeve is movable radially with respect to the retainer sleeve. The lock member can engage the shank of the tool bit to limit axial movement of the tool bit. A small-diameter surface portion formed by an inner surface of a fixed front cover contacts the rock member and projects at least part of the lock member inward of the retainer sleeve to engage the lock member with the shank of the tool bit when the retainer sleeve is placed at an active position. A conic surface portion formed by the inner surface of the front cover is engageable with the lock member, and is able to variably limit radial movement of the lock member as the retainer sleeve moves axially.

Abstract: A hammer holder, provided between a retainer sleeve and a cylinder, slidably holds an intermediate member in an axial direction. A predetermined clearance is maintained between the hammer holder and the retainer sleeve. The hammer holder has a recessed portion which is engageable with a flange of the intermediate member so as to restrict the slide movement of the intermediate member. A cushioning member receives a percussion force when the flange is stopped by the recessed portion. The clearance restricts a compression amount of the cushioning member so that a predetermined life of the cushioning member is assured.

Abstract: A tool bit holding device for use in percussion apparatuses such as electrically operated hammers is provided. The device includes a tool bit carrier, a front hand-operated grip, and a rear hand-operated grip. The front hand-operated grip is supported by the tool bit carrier so as to be movable in a lengthwise direction and a circumferential direction of the tool bit carrier. The rear hand-operated grip is installed rotatably on a hollow cylinder connected to a casing of the hammer. The removable of a tool bit from the tool bit carrier is accomplished by moving the front grip in the lengthwise direction and then turning it in the circumferential direction to release engagement between the tool bit and the tool bit carrier. The angular orientation of the tool bit carrier relative to the casing of the hammer is accomplished by turning the rear grip relative to the tool bit carrier to shift a angular relation between the tool bit carrier and the casing of the hammer.

Abstract: A vibration-damping apparatus for an electric hammer unit is provided. This vibration-damping apparatus is provided with the so-called transatory unit including elastic bars disposed between elastic damper members connected to a tool body and a handle of the electric hammer unit, respectively, for absorbing relative displacement of the elastic damper members caused by vibrations produced by the tool body during use. The vibration-damping apparatus further includes a stopper member attached to the elastic damper member attached to the handle so as to engage a chamber formed in the elastic damper member attached to the tool body for preventing the handle from being dislodged from the tool body even when the handle is swung laterally by a hammer operator.