A power tool comprising a housing, a motor, and a circuit board residing in the housing is provided. A rectifier that receives an alternating current and converts the alternating current to a direct current, a switching arrangement having a plurality of motor switches connected electrically between the rectifier and the motor, and a capacitor connected electrically between the rectifier and the switching arrangement, are mounted on a rear portion of a planar surface of the circuit board. A switching arrangement and at least one heat sink in thermal communication therewith are mounted on a front portion of the planar surface of the circuit board.

A power tool comprising a housing, a motor, and a circuit board residing in the housing is provided. A rectifier that receives an alternating current and converts the alternating current to a direct current, a switching arrangement having a plurality of motor switches connected electrically between the rectifier and the motor, and a capacitor connected electrically between the rectifier and the switching arrangement, are mounted on a rear portion of a planar surface of the circuit board. A switching arrangement and at least one heat sink in thermal communication therewith are mounted on a front portion of the planar surface of the circuit board.

An end face polishing device for optical fiber ferrule for polishing an end face of an optical fiber ferrule by applying a polishing pressure between a polishing plate driven by a polishing drive shaft and an optical fiber ferrule held by a holding portion. The end face polishing device has: a bearing portion for allowing the polishing plate to rotate relatively around the polishing drive shaft and to move relatively to the polishing drive shaft in an axial direction; a polishing plate guide supporting portion for movably supporting the polishing plate on a base portion to apply the polishing pressure to the holding portion by allowing the polishing plate to move in the axial direction; a pressing drive source for outputting a driving force to apply the polishing pressure; and a pressing force transmission mechanism for transmitting the driving force output from the pressing drive source as a pressing force in the axial movement direction of the polishing plate.

An end face polishing device for optical fiber ferrule for polishing an end face of an optical fiber ferrule by applying a polishing pressure between a polishing plate driven by a polishing drive shaft and an optical fiber ferrule held by a holding portion. The end face polishing device has: a bearing portion for allowing the polishing plate to rotate relatively around the polishing drive shaft and to move relatively to the polishing drive shaft in an axial direction; a polishing plate guide supporting portion for movably supporting the polishing plate on a base portion to apply the polishing pressure to the holding portion by allowing the polishing plate to move in the axial direction; a pressing drive source for outputting a driving force to apply the polishing pressure; and a pressing force transmission mechanism for transmitting the driving force output from the pressing drive source as a pressing force in the axial movement direction of the polishing plate.

A power tool includes a three-phase DC motor, a power switching network, a power source, and an electronic processor. A first phase of the motor is connected between a first low side electronic switch and a power source electronic switch, and connected to the power source via a first high side electronic switch in parallel with a diode. The electronic processor is configured to receive an indication to stop the motor during operation of the motor and activate the first low side electronic switch and a second low side electronic switch for a first predetermined time responsive to receiving the indication such that a back-electromagnetic force generated by the motor is stored in the first phase. The electronic processor is configured to deactivate the second low side electronic switch after the first predetermined time such that a first regenerative current is provided to the power source via the diode.

An electric tool includes an output member, a motor, and a housing. The motor includes a rotor shaft, a rotor core, and a stator component. The rotor shaft is configured to rotate around a first axis. The stator component includes a coil winding. The stator component surrounds the first axis to separate the accommodation cavity into a first space and a second space. The first space includes a first end and a second end. The motor further includes a first end cover and a second end cover. The first end cover is disposed at the first end of the first space. The second end cover is disposed at the second end of the first space. A passage is formed between the second end cover and a structure surrounding the first space, and the passage is configured to place the first space into communication with the second space.

An electric tool includes an output member, a motor, and a housing. The motor includes a rotor shaft, a rotor core, and a stator component. The rotor shaft is configured to rotate around a first axis. The stator component includes a coil winding. The stator component surrounds the first axis to separate the accommodation cavity into a first space and a second space. The first space includes a first end and a second end. The motor further includes a first end cover and a second end cover. The first end cover is disposed at the first end of the first space. The second end cover is disposed at the second end of the first space. A passage is formed between the second end cover and a structure surrounding the first space, and the passage is configured to place the first space into communication with the second space.

A plane polishing machine polishing one surface of a workpiece flat, the plane polishing machine comprises a stick-on disk decentering jig of a circular plate shape mounted on a rotating polishing surface plate, a jig rotation drive device having a plurality of guide rollers coming into contact with the stick-on disk decentering jig, a rotational direction restriction device permitting rotation of the stick-on disk in a direction identical to a rotational direction of the stick-on disk decentering jig and inhibiting rotation of the stick-on disk in a direction opposite to the rotational direction of the stick-on disk decentering jig, and a jig rotation suppression device periodically suppressing rotation of the stick-on disk decentering jig rotated by the drive guide roller, for a predetermined period.

A plane polishing machine polishing one surface of a workpiece flat, the plane polishing machine comprises a stick-on disk decentering jig of a circular plate shape mounted on a rotating polishing surface plate, a jig rotation drive device having a plurality of guide rollers coming into contact with the stick-on disk decentering jig, a rotational direction restriction device permitting rotation of the stick-on disk in a direction identical to a rotational direction of the stick-on disk decentering jig and inhibiting rotation of the stick-on disk in a direction opposite to the rotational direction of the stick-on disk decentering jig, and a jig rotation suppression device periodically suppressing rotation of the stick-on disk decentering jig rotated by the drive guide roller, for a predetermined period.

Provided is a power tool capable of performing braking in which deterioration and breakage of elements are inhibited. In a brake control, an arithmetic unit 21: performs a switching control of a combination of any of upper arm side Q1-Q3 switching elements and any of lower arm side switching elements Q4-Q6 while sequentially switching the elements; and causes a current to flow in a closed loop (a closed loop in the same direction as during driving of the power tool) in order through any of the upper arm side Q1-Q3 switching elements, stator coils 6e, any of the lower arm side switching elements Q4-Q6, and a first diode bridge 15.