Abstract: In order to permit the removal of tachogenerator elements during maintenance services performed on the machinery, the magnet assembly of the tachogenerator is stationary, and soft iron core elements are affixed to the rotating shaft of the machinery. For servicing the machinery, the core elements may be removed without disturbing the alignment or calibration of the magnet assembly.

Abstract: A drill chuck arrangement for connecting a drill bit to a spindle of a drilling machine comprises a spindle member threaded onto the spindle, and a jaw-actuating member mounted at least in part about the spindle member for concentric turning about the latter. A plurality of opposed clamping jaws are movable towards and away from each other in response to the aforementioned concentric turning. The spindle member has a radial bore which receives a portion of an actuating tool having beveled gear means. Upon turning the tool, the beveled gear meshes with a cooperating gear on the jaw-actuating member so as to turn the same relative to the spindle member, and thereby clamp or release a drill bit inserted in between the clamping jaws. A bushing is provided intermediate the spindle member and the jaw-actuating member to prevent binding between these members.

Abstract: An energy limiting circuit for the operating stroke of a motor-driven screwdriver energized by alternating current is activated in response to a pulse of current amplitude, which may be the starting current of the motor or the first of a series of current amplitude pulses characteristic of screw tightening impacts produced by an impact-type screwdriver. The energy limiting circuit in a simple case is a timing circuit. For operation with strict reference to the impacting energy, the energy limiting circuit is a pulse counter. Adjustment of the timing or of the pulse counting is provided for setting the tool to the conditions of a particular repetitive task.

Abstract: To reduce noise and idling speed of electric motors, particularly series motors, the speed-torque characteristic of the motor is dropped with respect to the loaded speed-torque characteristic, by sensing no-load operation of the motor and deriving a sensed signal, the sensed signal being applied to controlled switches to abruptly change the effective voltage applied to the motor between values corresponding to the no-load speed-torque characteristic, or the load speed-torque characteristic and resulting in the desired speed, in dependence on the value of the sensed signal. Preferably, the operating condition of the motor is sensed by an inductive transducer, and a speed change is obtained by phase control, or half-wave rectification.