A machine tool includes a tool and a protective device. The tool includes a saw blade and a motor for driving the saw blade. An insulating member is arranged between the saw blade and the motor. The protective device includes a signal receiving unit, a control unit and a breaker. The signal receiving unit has an antenna receiving end that is in electrical contact with a middle region of the saw blade. The breaker is electrically connected between the motor and a utility power supply. The control unit is connected to the signal receiving unit and the breaker. The saw blade is used as an antenna by the signal receiving unit to receive an electromagnetic wave having the same frequency as that of a utility power from an environment, and the control unit controls the breaker according to a change of intensity in the electromagnetic wave.

A safety system for a power tool having a motor and a cutting tool driven by the motor includes a control device configured to detect a direct contact of a conductive material with the cutting tool, the direct contact of the conductive material with the cutting tool defining a contact event, and a braking device movable between a retracted position and an engaged position. The control device is configured to interrupt electrical power to the motor and control the braking device to the engaged position when the contact event is detected.

Wall saw having a locking device (41). A saw blade flange (25) of the wall saw is adjustable by the locking device (41) between a locked state and an unlocked state, wherein, in the locked state, the saw blade flange (25) is connected to the drive spindle (33) for rotation therewith, and, in the unlocked state, is adjustable in relation to the drive spindle (33). In the unlocked state of the saw blade flange, the drive spindle is blocked in the direction of rotation of the saw blade and is designed to be rotatable about the axis of rotation in a counter direction directed counter to the direction of rotation.

Twisting of a locking member due to cogging torque is reduced without lowering the locking and unlocking operability for a user. A power tool includes a housing, an electric motor located inside the housing and including a permanent magnet, a shaft rotatable about an axis relative to the housing to transmit power from the electric motor, a locking member movable between a lock position and an unlock position in a nonenergized state of the electric motor and engageable with the shaft at the lock position to lock rotation of the shaft, and an abutting member that applies, to the locking member at the lock position, a force in a direction opposite to an axial torque caused by the permanent magnet and applied to the locking member.

Fast-acting and low-inertia actuators useable in various applications where a high force must be applied very quickly are disclosed. Power tools with detection systems configured to detect a dangerous condition between a person and a cutting tool are disclosed. In power tools, for example in a woodworking machine, a fast-acting and low-inertial actuator as disclosed herein can be used to retract a blade upon detection of a dangerous condition by a detection system. The actuator includes a charge of pressurized fluid and one or more electromagnets to selectively retain or release the pressurized fluid.

Fast-acting and low-inertia actuators useable in various applications where a high force must be applied very quickly are disclosed. Power tools with detection systems configured to detect a dangerous condition between a person and a cutting tool are disclosed. In power tools, for example in a woodworking machine, a fast-acting and low-inertial actuator as disclosed herein can be used to retract a blade upon detection of a dangerous condition by a detection system. The actuator includes a charge of pressurized fluid and one or more electromagnets to selectively retain or release the pressurized fluid.

A work apparatus has a drive motor and a work tool driven in a rotating manner by the drive motor. The work tool is at least partially covered by a protective hood which is mounted pivotably about the rotational axis of the work tool. A control unit is provided for controlling at least one component of the work apparatus. The work apparatus has a detection unit for detecting at least one position of the protective hood. The control unit is configured for controlling the at least one component of the work apparatus depending on the detected position of the protective hood. In a method for operating a work apparatus, the detection unit detects at least one position of the protective hood and supplies the information to the control unit. The control unit activates the at least one component depending on the detected position of the protective hood.

A work apparatus has a drive motor and a work tool driven in a rotating manner by the drive motor. The work tool is at least partially covered by a protective hood which is mounted pivotably about the rotational axis of the work tool. A control unit is provided for controlling at least one component of the work apparatus. The work apparatus has a detection unit for detecting at least one position of the protective hood. The control unit is configured for controlling the at least one component of the work apparatus depending on the detected position of the protective hood. In a method for operating a work apparatus, the detection unit detects at least one position of the protective hood and supplies the information to the control unit. The control unit activates the at least one component depending on the detected position of the protective hood.

A work apparatus has a work tool driven by a combustion engine. A brake assembly has a brake element for braking the work tool as it slows down. In a braking position of the brake assembly, the work tool is braked, while, in a stand-by position of the brake assembly, the brake element enables the movement of the work tool. The brake element is held in the stand-by position by a holding force from an electromagnet supplied with energy by an electric generator driven by the engine, for which purpose, in the stand-by position of the brake assembly, a holding current is supplied to the electromagnet. To extend the holding time as the engine slows down, an operating parameter of the engine is monitored and, after a limit value of the operating parameter is reached, the holding current supplied to the electromagnet is reduced.

A work apparatus has a work tool driven by a combustion engine. A brake assembly has a brake element for braking the work tool as it slows down. In a braking position of the brake assembly, the work tool is braked, while, in a stand-by position of the brake assembly, the brake element enables the movement of the work tool. The brake element is held in the stand-by position by a holding force from an electromagnet supplied with energy by an electric generator driven by the engine, for which purpose, in the stand-by position of the brake assembly, a holding current is supplied to the electromagnet. To extend the holding time as the engine slows down, an operating parameter of the engine is monitored and, after a limit value of the operating parameter is reached, the holding current supplied to the electromagnet is reduced.