A limit switch assembly in combination with a plurality of mobile storage units, said limit switch assembly comprising:
- a base member,
- rod means having opposite ends and mounted on said base member for moving axially between a first limit position wherein one end is fully projected a predetermined distance from said base member and a second limit position wherein said rod means is retracted relative to said base member,
- switch operating cam means fixed on said rod means for moving therewith between corresponding limit positions, said cam means including axially spaced apart first and second cam surfaces,
- first and second axially spaced apart switches mounted adjacent said rod means for said first cam surface on said rod means to operate the first switch when said first cam surface is in the first limit position and to operate the second switch when the second cam surface is in said second limit position, and
- means for applying a biasing force to said rod means to move said first cam surface thereon to said first limit position wherein said one end of said rod means projects by said predetermined distance and said first cam surface operates said first switch, and such that a force acting on said rod means to overcome said biasing force retracts said rod means for said second cam surface to operate said second switch,
- said plurality of mobile storage units arranged in a row, said units being adapted for being moved in appropriate directions for opening an aisle between any two of them or between one of them and a stationary object such as a stationary storage unit,
- said mobile storage units each having wheels for moving on tracks, a reversible electric motor for driving the unit, a push button switch operative to produce signals for commanding movements of said mobile storage units to open an aisle and an electrical controller also on each mobile storage unit responsible to a command signal from one of said push button switches by causing the motor on the storage unit containing the associated controller to drive respective mobile storage units in directions which result in said aisle opening,
- at least one of said limit switch assemblies mounted to each of said mobile storage units with said rod means axes aligned in the direction in which said mobile storage units are constrained to move bidirectionally on said tracks, the rod means of the limit switch assembly on the leading mobile storage unit adjacent an open aisle is in said first limit position wherein said one end is fully projected and said cam means disposing said first limit switch in closed circuit condition, and the rod means of the next trailing storage unit is retracted as a result of contact with said leading storage unit,
- said electrical controllers responding to a signal commanding movement of said storage units to achieve closing of said open aisle and opening of another aisle by turning on the electric motor on said leading mobile storage unit for it to start accelerating in the direction to close said aisle,
- slight amount of movement of said leading mobile storage unit allowing the retracted rod means in the limit switch assembly of said next trailing mobile storage unit to initiate projecting such that the cam means on the rod means of the trailing mobile storage unit moves simultaneously by said slight amount to cause said second switch to change to a closed circuit condition to which the controller responds by energizing the motor on said trailing storage unit for the unit to begin accelerating in the direction to close said aisle while the leading mobile storage unit is still accelerating.