Deflection gate driven by stepper motor

Claim 1

Sorting apparatus comprising a deflector movable between first and second positions and located in a path of movement of the articles to be sorted, the position of the deflector ensuring that each article will follow one of two paths; and means for positioning the deflector, the positioning means including: a stepping motor having two windings which are connected in parallel between two transistor circuits, each of which comprises two series-connected transistors; a circuit for energising the stepping motor for angular movement in a first direction or in a second opposite direction; means limiting the angular movement of the stepping motor shaft to a first angular position in one direction and a second angular position in the other direction, the angular interval between the first and second angular positions being less than and lying within the angular interval defined by a shaft position of stable equilibrium in the first direction of energisation of the stepping motor windings and an immediately adjacent shaft position of stable equilibrium in the second direction of energisation of the stepping motor windings; and means coupling the shaft of the stepping motor to the deflector such that the deflector is in its first and second positions when the stepping motor shaft is in its first and second angular positions, respectively; and wherein the control circuit is connected to receive a binary signal representing the required direction of rotation of the stepping motor and providing two output signals of opposite logic levels, the conductivity types of the transistors and the connections from the outputs of the control circuit to the transistor gates being such that when said binary signal is at a first logic level current flows through the two windings in a first direction and when said binary signal is at a second logic level current flows through the two windings in the opposite direction.