An electric power tool includes an output shaft, drivable by an associated drive motor, and a brake apparatus for braking the output shaft rotating in the unpowered state of the associated drive motor. The output shaft is mounted in a rotatable manner in an associated housing and the brake apparatus has a magnetic-field brake unit with at least one first and one second brake element. The first brake element is arranged radially with respect to the output shaft in a rotationally fixed manner in the associated housing and includes at least one first and one second magnetic pole configured to generate a magnetic field that alternates in the circumferential direction of the output shaft. The second brake element is magnetically conductive and rotationally connected to the output shaft via an activatable coupling device.

In a substrate polishing apparatus where a polishing liquid passes through inside a rotary joint, the rotary joint requires maintenance. There is provided a substrate polishing apparatus that includes: a polishing head for holding a substrate; a rotary table that has a surface to which a first opening portion is provided; a polishing liquid discharge mechanism disposed to the rotary table; and a controller configured to control at least the polishing liquid discharge mechanism. The polishing liquid discharge mechanism includes a first cylinder, a first piston, and a driving mechanism that drives the first piston. The first opening portion is communicated with a liquid holding space defined by the first cylinder and the first piston. The controller controls the driving of the first piston by the driving mechanism to increase and decrease a volume of the liquid holding space.

A sander, in particular a battery-operated sander, preferably an orbital sander or random orbital sander having a tool holder, in particular a sanding pad, includes a drive unit for driving the tool holder and a housing unit having a bow-shaped handle. A ratio between a maximum longitudinal extent of a handle recess of the bow-shaped handle and a maximum longitudinal extent of the tool holder is at least 0.35 and at most 0.5.

A sander, in particular a battery-operated sander, preferably an orbital sander or random orbital sander having a tool holder, in particular a sanding pad, includes a drive unit for driving the tool holder and a housing unit having a bow-shaped handle. A ratio between a maximum longitudinal extent of a handle recess of the bow-shaped handle and a maximum longitudinal extent of the tool holder is at least 0.35 and at most 0.5.

A random orbital sanding tool includes a power motor, a driving spindle connected to the power motor, an eccentric block connected to the driving spindle, a tool holder disposed on the eccentric block, and a sanding pad connected to the tool holder and indirectly driven by the power motor. The random orbital sanding tool includes a friction ring disposed on the tool holder, the friction ring contacts a surface of the eccentric block facing the sanding pad, the friction ring stops rotation of the tool holder and the sanding pad by a friction force exerting on the surface of the eccentric block when the power motor stops operation, the friction ring includes a base part protruding into a gap between the tool holder and the eccentric block, a sleeve part diverged and extended from the base part.

A random orbital sanding tool includes a power motor, a driving spindle connected to the power motor, an eccentric block connected to the driving spindle, a tool holder disposed on the eccentric block, and a sanding pad connected to the tool holder and indirectly driven by the power motor. The random orbital sanding tool includes a friction ring disposed on the tool holder, the friction ring contacts a surface of the eccentric block facing the sanding pad, the friction ring stops rotation of the tool holder and the sanding pad by a friction force exerting on the surface of the eccentric block when the power motor stops operation, the friction ring includes a base part protruding into a gap between the tool holder and the eccentric block, a sleeve part diverged and extended from the base part.

To provide a work tool capable of suppress temperature rise in a motor or a switching element. The work tool includes: a motor; a switching element switchable between an ON-state and an OFF-state, the switching element allowing a current to flow through the motor during the ON-state, the switching element prohibiting a current from flowing through the motor during the OFF-state; target rotation number setting means for setting a target rotation number of the motor; rotation number controlling means for controlling the motor such that the rotation number thereof is brought in coincidence with the target rotation number by changing an ON-duration, during which the switching element is in the ON-state, in one switching period of the switching element; and temperature detecting means for detecting at least one of a temperature of the motor and a temperature of the switching element. The rotation number controlling means is capable of setting an upper limit with respect to the ON-duration on the basis of the temperature detected by the temperature detecting means and changes the ON-duration within a range not more than the upper limit.

The invention relates to a device with a machine tool and a braking device, the machine tool having an eccentrically supported, rotatable backing pad for receiving a tool. According to one embodiment, the braking device has a frame, which is attached to the machine tool; a spring, a first end of which is fixed on the frame; and a lever, which is connected to a second end of the spring. The braking device also has an actuator, which is designed to move the lever, wherein in the event of a movement of the lever, the spring is compressed and a part of the lever is pressed against the backing pad of the machine tool.

The invention relates to a device with a machine tool and a braking device, the machine tool having an eccentrically supported, rotatable backing pad for receiving a tool. According to one embodiment, the braking device has a frame, which is attached to the machine tool; a spring, a first end of which is fixed on the frame; and a lever, which is connected to a second end of the spring. The braking device also has an actuator, which is designed to move the lever, wherein in the event of a movement of the lever, the spring is compressed and a part of the lever is pressed against the backing pad of the machine tool.

A grinding machine tool comprises a housing, a driving assembly disposed in the housing, a grinding disc driven by the driving assembly, and having a grinding surface and a non-grinding surface, a switch driving the driving assembly, and a pressing plate disposed on the housing and having a first state in which the switch drives the driving assembly to drive the grinding disc when the pressing plate is operated, and a second state in which the switch stops driving the driving assembly when the pressing plate is not operated. The grinding machine tool has a grinding disc braking structure detached from the non-grinding surface when the pressing plate is in the first state; when the pressing plate is in the second state, the grinding disc braking structure moves toward the non-grinding surface and contacts with the grinding disc to stop the grinding disc from rotating.