An apparatus and a method is described for smoothing the acceleration and deceleration of an electric motor. This is accomplished by using a pair of brush springs (strong and weak) for each brush of an electric motor. At low speeds, the strong spring is retracted so that the force with which the brush is applied to the motor commutator is greatly reduced. This reduced frictional force improves the smoothness of the acceleration and deceleration characteristics of the motor at low speeds.

A power assisted manually operated vehicle wherein the power assist is capable of providing different power and speed curves depending upon the operating condition. The operator may also select one of these conditions for manual operation such as to obtain an assist when pushing the vehicle. The variable speed and power curves are obtained with a permanent magnet electric motor with the variations being obtained by varying the field strength of the permanent magnet through an augmenting coil.

A motor or generator having a commutator and brushes for transfer of current to and from rotor windings has a stationary conducting sensor in sliding contact with the commutator, said sensor being narrower at its contact with the commutator than the insulation between the commutator bars where contacted by the sensor, so that a sensing circuit is interrupted between the sensor and one of the brushes at a frequency proportional to the speed of the rotor.

A method and a device for controlling a brush-commutator assembly of a machine under application of an electrical processing and control unit, by sensing one or more operating parameters of the electric machine, the sensing values being processed and converted into one or more control signals controlling the operation of the brush-commutator assembly to provide an optimal commutation process of the machine current. The machine current is sensed and the pressing exerted on the brushes is controlled by a fluid under pressure; the brush tracks, moreover, being engaged and disengaged upon increase and decrease of the machine current respectively in order to maintain an optimal current density in the brushes. One or more sensors for sensing operating parameters of the electric machine are used and a processing and control unit to process the signals sensed by the sensors and to supply control signals to one or more control means controlling the operation of the brush-commutator assembly. The control device comprises a fluid control circuit having an electrically controllable pressure system. The sensors are operable to detect the temperature of the cooling air and/or of the commutator, the humidity of the cooling air, the commutation noise on the machine current, the speed of revolutions, and extreme mechanical vibrations.

A coupler for optically connecting two lengths of dielectric optical waveguide has a plug and a socket. The socket consists of a sleeve having a first capillary bore tube rigidly fixed in the sleeve and a second capillary bore tube slidable in the sleeve. A length of dielectric optical waveguide is threaded through the first tube and partially threads the second tube. The plug consists of a capillary bore tube of similar cross-section to the second capillary bore tube, with a length of dielectric optical waveguide partially threading, and rigidly attached to the capillary bore tube. When the plug is inserted in the socket the second capillary tube slide back along the length of the dielectric optical waveguide which is thus guided into the plug capillary bore. A modification of the invention provides a plug and socket connection for simultaneously joining a large number of dielectric optical waveguides.