Abstract: A storage assembly in which a row of storage units, such as racks, are movable between fixed limits along the length of the row in either of two opposite directions so that a gangway can be provided between the sides of any two adjacent units, and in which each storage unit is provided with a set of reversible electric motors adapted to drive individual independently rotatable drive wheels to move that storage unit, and a set of switches is provided along each side of each storage unit so as to be operated by means at the side of an adjacent storage unit, each switch in each set being associated with a respective reversible motor in the vicinity of the switch so as to control operation of that motor independently of the others and to cut-off the supply of electricity to the motor when it is operated. Thus each motor will continue to operate to move the part of the unit by which it is carried until that part reaches a datum position defined by the side of an adjacent storage unit.

Abstract: Sensor means which is fitted to a mobile member so as to stop the latter on engagement with an object in its path comprising a trip bar, a plurality of links which are arranged at spaced points along the mobile member and are each pivotally connected to said mobile member and trip bar at respective opposite ends so that they form a folding parallelogram with the mobile member and trip bar, and switch means which is arranged in relation to said trip bar so as to be operated by movement of the latter towards said mobile member. Preferably, at least one of the links is pivotally connected to the mobile member by connection means which is adjustable in position along a respective portion of the length of the mobile member and which preferably carries a stop in a predetermined angular position relative to the pivot between the link and connection means so that the links lie parallel to one another when they engage their respective stops.