The invention relates to an emergency stop device for a power tool comprising an electrical power contact for releasably connecting a power source to the power tool, and an emergency stop circuit connected to the electrical power contact and configured to disconnect the electrical contact from the electrical power source upon receipt of an emergency stop signal by the emergency stop circuit. The invention further relates to a power tool, a system comprising such a tool and a method of performing emergency stop of a power tool.

A safety system is provided for a machine tool which has a frame and a tool. The safety system has a clamping device and a motion device. The clamping device is movable by the motion device from a working position, in which the tool is extended and can be used for working, to a safety position, in which the tool is retracted. The motion device has a first magnetic means connected to or arranged on the tool and a second magnetic means connected to or arranged on the frame, such that movement of the tool by the motion device from the working position to the safety position can be triggered and/or at least partially performed by magnetic force.

A power tool and methods are provided for detecting objects (e.g., flesh or other materials) in the operating path of a power tool's output component (e.g., saw blade or drill bit). An object detection sensor in the power tool generates an output signal indicative of a type of material detected in the operating path of the power tool. A power tool controller receives the object detection sensor output and determines when a material in the operating path of the power tool changes. The controller changes operation of a motor of the power tool (e.g., increasing or decreasing speed or stopping the motor) in response to the detected material change. The object detection sensor may include, for example, an RF sensor, a capacitive sensor, a camera, a conductivity probe, or an ultrasound probe.

A safety brake device for a power tool includes a decoupling device, configured to decouple an output unit from a drive unit during a braking operation thereby reducing at least one of a rotational mass and rotational energy of the output unit, and a brake device with a first brake device part and a second brake device part. The first brake device part is arranged on the output unit so as to allow essentially no relative rotation, and the second brake device part is configured to allow essentially no relative rotation with respect to the power tool. The first brake device part and the second brake device part are configured to interact mechanically with one another during a braking operation to stop rotation of the output unit. The first brake device part of the brake device is embodied in one piece with the decoupling device.

A safety brake device for a power tool includes a decoupling device, configured to decouple an output unit from a drive unit during a braking operation thereby reducing at least one of a rotational mass and rotational energy of the output unit, and a brake device with a first brake device part and a second brake device part. The first brake device part is arranged on the output unit so as to allow essentially no relative rotation, and the second brake device part is configured to allow essentially no relative rotation with respect to the power tool. The first brake device part and the second brake device part are configured to interact mechanically with one another during a braking operation to stop rotation of the output unit. The first brake device part of the brake device is embodied in one piece with the decoupling device.

A safety brake device for braking a machining tool includes at least one brake device configured as an at least two-part claw clutch. The claw clutch includes a first claw-clutch part, and a second claw-clutch part. The first claw-clutch part is arranged on the output shaft so as to allow no relative rotation, the second claw-clutch part is configured to allow no relative rotation with respect to the power tool, each claw-clutch part has a respective plurality of toothing elements, the respective plurality of toothing elements are configured to engage with one another during a braking operation to stop rotation of the output shaft, and a maximum angular spacing Δmax of mutually adjacent toothing elements of at least one of the first plurality of toothing elements an the second plurality of toothing elements is determined depending on a maximum rotational speed of the output shaft.

An electric working machine comprises a motor, a switch, a drive device, a brake device, and a failure determiner. The switch is configured for operation by a user, has an on-state and an off-state. The drive device is configured to drive the motor in response to the switch being placed in the on-state. The brake device is configured to control deceleration of the motor to a stopped state in response to the switch being placed in the off-state. The failure determiner is configured to monitor deceleration of the motor during controlled deceleration and to determine whether the brake device has failed based on the monitored deceleration.

In an apparatus for detecting tip-over of a rammer equipped with a crankcase accommodating an output shaft rotatably connected to an engine, a movable unit accommodating a converter mechanism for converting rotation of the output shaft to vertical motion of a movable member, a tamping shoe connected to the movable unit, and a handle operable by an user, and adapted to thrust upward in the gravitational direction by the vertical motion of the movable member and go into a free fall to compact a ground surface, it is determined whether a detected engine speed becomes equal to or smaller than a threshold value set lower than an engine idling speed when the engine has been operated at a rammer working speed set greater than the engine idling speed, and if it does, it is discriminated that the rammer has tipped over.

A motor drive system is provided, which includes: an inverter coupled with two terminals of a power supply, where the inverter includes multiple semi-conductive switch elements and is configured to convert a voltage provided by the power supply to an alternating current to drive a motor; a microcontroller configured to output a drive signal to control an power mode of the semi-conductive switch elements in the inverter; and a rheostat coupled with the microcontroller and configured to provide an input signal to the microcontroller by sliding, where the microcontroller outputs a brake signal to the inverter to control the motor to stop operating when the input signal meets a predetermined condition, and the microcontroller is powered off when the motor stops rotating.

A grinder includes a brake mechanism configured to brake a spindle and an electrical actuator (a solenoid) that actuates the brake mechanism. The solenoid actuates the brake mechanism in conjunction with a turning OFF of a switch from a driving state of a motor, and releases an actuation of the brake mechanism after a lapse of a predetermined period of time from the turning OFF of the switch.