Power tool

A power tool includes an electric motor having an output shaft, a transmission having a transmission housing, a spindle rotatable in response to receiving torque from the transmission and a pinion coupled to the output shaft. The pinion includes a bushing portion, a toothed portion for driving the transmission, and a cylindrical portion between the bushing portion and the toothed portion. The power tool further comprises a fan coupled to the bushing portion of the pinion and a bearing arranged between the cylindrical portion and the transmission housing for rotatably supporting the pinion and the output shaft.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly to power tool drive assemblies.

BACKGROUND OF THE INVENTION

Power tools include electric motors having an output shaft to which a pinion is attached to transfer torque from the motor to a transmission. Fans are sometimes rotatably coupled to the output shaft to cool the motor as the output shaft rotates.

SUMMARY OF THE INVENTION

The present invention provides, in one aspect, a power tool comprising an electric motor including an output shaft, a transmission including a transmission housing, a spindle rotatable in response to receiving torque from the transmission, and a pinion coupled to the output shaft. The pinion includes a bushing portion, a toothed portion for driving the transmission, and a cylindrical portion between the bushing portion and the toothed portion. The rotary power tool also includes a fan coupled to the bushing portion of the pinion and a bearing arranged between the cylindrical portion and the transmission housing for rotatably supporting the pinion and the output shaft.

The present invention provides, in another aspect, a power tool comprising an electric motor including an output shaft, a transmission including a transmission housing, a spindle rotatable in response to receiving torque from the transmission, and a pinion coupled to the output shaft. The pinion includes a bushing portion including splines, a toothed portion for driving the transmission, and a cylindrical portion between the bushing portion and the toothed portion. The power tool further comprises a fan including corresponding splines that couple the fan to the splines of the bushing portion, such that the fan is coupled for co-rotation with the bushing portion. The power tool further comprises a bearing rotatably supporting the pinion and the output shaft. The bearing includes an inner race coupled to the cylindrical portion of the pinion, an outer race coupled to the transmission housing, and a plurality of rollers between the inner race and the outer race.

The present invention provides, in yet another aspect, a power tool comprising an electric motor including an output shaft, a transmission including a transmission housing and a plurality of planet gears, a spindle rotatable in response to receiving torque from the transmission, and a pinion coupled to the output shaft. The pinion includes a bushing portion including splines, a toothed portion extending through an opening in the transmission housing and meshed with the planet gears in the transmission housing, and a cylindrical portion between the bushing portion and the toothed portion. The power tool further comprises a fan including corresponding splines that couple the fan to the splines of the bushing portion, such that the fan is coupled for co-rotation with the bushing portion. The power tool also comprises a bearing rotatably supporting the pinion and the output shaft. The bearing includes an inner race coupled to the cylindrical portion of the pinion, an outer race positioned within a recess in the transmission housing adjacent the opening, and a plurality of rollers between the inner race and the outer race.

DETAILED DESCRIPTION

As shown schematically inFIG. 1, a power tool, such as a rotary power tool10, includes a housing14, a trigger16on the housing14, an electric motor18, a multi-stage planetary transmission22, and a spindle24that receives torque from the motor18via the transmission22when an operator presses the trigger16. As shown inFIG. 2, the motor18includes a stator26and a rotor30. In the illustrated embodiment, the rotor30includes a motor output shaft34extending from the stator26and a pinion42is coupled for co-rotation with the motor output shaft34(e.g., by an interference fit, a press-fit, etc.). In other embodiments such as the one shown inFIG. 4, the pinion42is integrally formed with the output shaft34.

As shown inFIGS. 2 and 3, the pinion42includes a bushing portion46, a toothed portion50, and a cylindrical portion54between the bushing portion46and the toothed portion50. The bushing portion46is configured to rotatably couple a fan58having blades60to the pinion42. In the illustrated embodiment, the bushing portion46includes splines62and the fan58includes corresponding splines64that engage the splines62of the bushing portion46as shown inFIG. 2A, thereby ensuring co-rotation of the fan58and the pinion42. The toothed portion50is configured as a sun gear that is meshed with multiple planet gears66of the multi-stage planetary transmission22. The transmission22includes a transmission housing70that has an opening74through which the toothed portion50of the pinion42extends.

On a side of the transmission housing70facing the motor18, the transmission housing70defines a recess78for receiving a bearing82having an inner race86, an outer race90, and a plurality of rollers94between the inner and outer races86,90. The bearing82is arranged on the cylindrical portion54of the pinion42for rotatably supporting the pinion42and the output shaft34on the transmission housing70, which in turn is supported by the power tool housing14. In some embodiments, the inner race86is interference or press-fit to the cylindrical portion54and the outer race90is slip-fit to the transmission housing70within the recess78.

In operation, an operator presses the trigger16of the power tool10, which activates the motor18and causes the output shaft34and the pinion42to rotate. The fan58is also caused to rotate via its connection with the bushing portion46, resulting in the blades60creating a cooling airflow through the motor18. As the pinion42rotates, the rotating toothed portion50drives the planet gears of the transmission22, ultimately causing the spindle24to rotate in response to receiving torque from the transmission22.