Abstract: There is disclosed a motion picture projector with self-threading mechanism with which has been combined automatic electric clutch and brake means for forward and reverse operations to permit the projector to be used in a search mode, an automatic film tension control means, an automatic lower-loop setter, a switch for stopping the projector upon loss of the upper loop, a frame counter and a pre-threaded projection magazine which fits over the reel arms and threads in the same manner as the conventional reels. The projector has in the front panel of its enclosure a slot into which is insertable a length of film extending between the two reels of the projector. After dropping a length of film into the slot the lever is pivoted from its leading position into its threading position. While being so pivoted, the lever sequentially causes locking of the film to the take-up sprocket, then to the supply sprocket, then forming the lower loop, then the upper loop, and finally pressing the film into the film channel.

Abstract: In a magnetic clutch a rotatable axially transferrable input disc which is part of a magnetic flux path including a magnetic cup in the output structure, engages annular friction surfaces on the output structure when magnetic flux is generated in the flux path by a coil. The friction surfaces are part of a rotatable coil and a magnetic cup attached to the driven shaft about which the input disc rotates freely in the absence of flux. The frictional torque generated by the engagement of the disc and the friction surfaces is proportional to the voltage applied to the flux-producing coil. When the input disc is locked, application of flux results in a braking action on the driven shaft.