Abstract: A power tool providing a smooth cooling air flow discharging through discharge windows formed in a housing. In the housing a radial fan is rotatably provided for cooling a heated motor. A cooling air generated by the radial fan is discharged through the discharge windows. Each discharge window has a rectangular shape having an upstream side and a downstream side in the rotating direction of the cooling fan. A chamfered portion is provided at least at the upstream side and in an inner peripheral surface of the housing, so that a thickness of the housing wall is gradually small in the rotating direction. The chamfered portion increases an effective area of the window for discharging air.

Abstract: A combustion-powered nail gun includes a housing, a combustion chamber wall, and a blocking member. The combustion chamber wall is disposed within the housing. The combustion chamber wall has an inner surface that defines a combustion chamber and an outer surface that is separated from the inner surface of the housing by a space. The combustion chamber wall has an inlet in its upper end and an outlet in its lower end. The combustion chamber wall moves vertically within the housing between an open position wherein the inlet and the outlet are opened and a sealed position wherein the inlet and the outlet are closed. The blocking member is provided for preventing flow of air through the space between the inner surface of the housing and outer surface of the combustion chamber.

Abstract: In a motor-driven tool, a carbon brush part 8 is arranged between a suction port 6 and a commutator 11 of the motor and includes a cylindrical side wall 8a. The cylindrical side wall 8a located on an outer periphery of the commutator 11 is provided with a tapered portion 8b which grows wider toward the commutator 11 and grows narrower toward a coil end 10 of the armature. Between the carbon brush part 8 and the coil end 10, there is provided a heat radiating plate 4 made of metal and adapted to be engaged with the carbon brush part 8.

Abstract: In a motor-driven tool, a carbon brush part 8 is arranged between a suction port 6 and a commutator 11 of the motor and includes a cylindrical side wall 8a. The cylindrical side wall 8a located on an outer periphery of the commutator 11 is provided with a tapered portion 8b which grows wider toward the commutator 11 and grows narrower toward a coil end 10 of the armature. Between the carbon brush part 8 and the coil end 10, there is provided a heat radiating plate 4 made of metal and adapted to be engaged with the carbon brush part 8.

Abstract: A combustion-powered nail gun includes a housing, a combustion chamber wall, and a blocking member. The combustion chamber wall is disposed within the housing. The combustion chamber wall has an inner surface that defines a combustion chamber and an outer surface that is separated from the inner surface of the housing by a space. The combustion chamber wall has an inlet in its upper end and an outlet in its lower end. The combustion chamber wall moves vertically within the housing between an open position wherein the inlet and the outlet are opened and a sealed position wherein the inlet and the outlet are closed. The blocking member is provided for preventing flow of air through the space between the inner surface of the housing and outer surface of the combustion chamber.

Abstract: A power tool providing a smooth cooling air flow discharging through discharge windows formed in a housing. In the housing a radial fan is rotatably provided for cooling a heated motor. A cooling air generated by the radial fan is discharged through the discharge windows. Each discharge window has a rectangular shape having an upstream side and a downstream side in the rotating direction of the cooling fan. A chamfered portion is provided at least at the upstream side and in an inner peripheral surface of the housing, so that a thickness of the housing wall is gradually small in the rotating direction. The chamfered portion increases an effective area of the window for discharging air.

Abstract: In a motor-driven tool, a carbon brush part 8 is arranged between a suction port 6 and a commutator 11 of the motor and includes a cylindrical side wall 8a. The cylindrical side wall 8a located on an outer periphery of the commutator 11 is provided with a tapered portion 8b which grows wider toward the commutator 11 and grows narrower toward a coil end 10 of the armature. Between the carbon brush part 8 and the coil end 10, there is provided a heat radiating plate 4 made of metal and adapted to be engaged with the carbon brush part 8.

Abstract: A power tool includes an impact damping mechanism for damping an impact in a direction of rotation of a speed reduction mechanism portion 8.

Abstract: A centrifuge includes a rotor and a drive device for rotating the rotor. A support frame is located between the rotor and the drive device. A viscoelastic member is provided between the support frame and the drive device. A locating device operates for locating the drive device in an axial direction. The locating device may include a suspension connecting the support frame and a bottom of the drive device. Preferably, the suspension includes one of a wire rope and a piano wire.

Abstract: A ball balancer for minimizing a dynamic unbalance of a moving part of a rotating machine such as a centrifuge is provided. The ball balancer includes a rotary balancer casing having disposed therein balls. The rotary balancer casing is mounted on the moving part coaxially with an axis of rotation thereof and has formed therein an inner side wall which is so curved that the balls are lifted away from the bottom of the balancer casing along the inner side wall by the centrifugal force and biased toward the opposite side of an unbalanced mass of the moving part when the rotational speed of the moving part exceeds a resonant speed that is a rotational speed of the moving part when matched with a natural frequency of the moving part, thereby counterbalancing the unbalanced mass of the moving part. In an alternative form, the balls include a first group having a large diameter and a second group having a small diameter. The large-diameter balls and the small-diameter balls are arranged alternately.

Abstract: A combustion gas powered tool includes a member defining a part of cylindrical combustion chamber having an axis. A piston is movable in a direction along the axis of the combustion chamber. The piston defines the combustion chamber in conjunction with the member. A mixture of air and fuel is generated in the combustion chamber. The air-fuel mixture in the combustion chamber is burned to drive the piston. An orifice grille extends in the combustion chamber, and is parallel to the axis of the combustion chamber.

Abstract: A combustion gas powered fastener driving tool includes inlet and outlet openings through which the combustion gases are discharged from a combustion chamber. These openings are located above the uppermost driving position (top dead center) of a slidable piston, so that an air and fuel mixture is fully trapped in the combustion chamber until after it is combusted. Since an outflow of the unburnt air and fuel mixture is completely prevented, the rate of fuel consumption of the fastener driving tool is high and there is no danger of accidental explosion of unburned fuel even when the fastener driving tool is used in a badly ventilated working place or site. An electric fan for forcing fresh air into the combustion chamber is disposed outside the cylinder and isolated from high temperatures. The fan is durable in structure and reliable in operation.

Abstract: A vibroisolating handle joint structure for a power tool such as a disc grinder has a vibratable power tool unit, a tubular handle holder fastened to the power tool unit and having first axial surfaces, a grip handle having on one end thereof a larger-diameter cup disposed radially around the handle holder and having second axial surfaces extending in substantially axially confronting relation to the first axial surfaces, and elastic members disposed between and joined to the first and second axial surfaces. The power tool unit and the handle are thus interconnected by the elastic members in a vibroisolating manner without using metallic plates. Even when some of the elastic members are torn apart, the power tool unit and the handle are prevented from being separated from each other by the first and second axial surfaces which are engageable with each other.

Abstract: A vibroisolating handle joint structure for a power tool such as a disc grinder has a vibratable power tool unit, a tubular handle holder fastened to the power tool unit and having first axial surfaces, a grip handle having on one end thereof a larger-diameter cup disposed radially around the handle holder and having second axial surfaces extending in substantially axially confronting relation to the first axial surfaces, and elastic members disposed between and joined to the first and second axial surfaces. The power tool unit and the handle are thus interconnected by the elastic members in a vibroisolating manner without using metallic plates. Even when some of the elastic members are torn apart, the power tool unit and the handle are prevented from being separated from each other by the first and second axial surfaces which are engageable with each other.

Abstract: In an internal-combustion piston driving apparatus comprising a housing, a cylinder cover fixed to the housing, a cylinder slidably provided to the housing, a piston reciprocally slidably provided in the cylinder, a combustion chamber defined by the housing, the cylinder, and the piston, a fuel supplying device for supplying fuel to the combustion chamber, and an ignition control device for producing a high voltage to ignite the fuel supplied to the combustion chamber, piston position detector for detecting a position of the piston is provided at the wall of the cylinder between top dead point and bottom dead point of the piston. Besides, a decompression channel is provided so as to connect the combustion chamber placed upper than the top dead point with atmosphere for exhausting a combusted gas in the combustion chamber when the piston passes the piston position detector. The decompression channel is opened and closed by means of slide of the cylinder.

Abstract: A housing partially defines a combustion chamber. A movable piston partially defines the combustion chamber. An air and fuel mixture is generated in the combustion chamber. The air and fuel mixture is ignited in the combustion chamber. An obstacle member is fixedly disposed in the combustion chamber. The obstacle member serves to generate turbulence in an unburned portion of the air and fuel mixture after the air and fuel mixture is ignited. Fuel may be injected into at least two points in the combustion chamber.