Abstract: A high thrust operator for gate valves employs an inverted satellite roller screw assembly driven by an internally threaded cylinder carried within a bearing case. The cylinder is sized to provide a relief plenum within the case into which the roller screw assembly can be over extended to expose tool engagement flats for attachment and release of a mating stem in the valve gate actuator.

Abstract: A runaway protection mechanism is provided which is truly nondestructive in nature and which is highly advantageous for an electric motor used in, for example, an exercise treadmill for driving its moving treadmill belt. In use, the electric motor is connected to an electric power source, such as an alternating-current wall outlet. The runaway protection mechanism includes a disconnect mechanism for disconnecting the motor from the electric power source and thereby deenergizing the motor. The runaway protection mechanism further includes a safety mechanism for comparing the actual motor speed with a desired motor speed and activating the disconnect mechanism when the actual speed exceeds the desired speed by a predetermined amount. In this manner, an orderly and nondestructive shutdown of the motor is accomplished when a fault condition is recognized.