Apparatus for generating a vacuum

Apparatus for engaging at least a portion of a signature in a hopper and moving the portion relative to a stack of signatures in the hopper, said apparatus comprising:

• a stem member pivotal toward and away from the stack of signatures in the hopper;
• a suction cup mounted on said stem member and movable with said stem member relative to the stack of signatures in the hopper;
• means for supporting said stem member for pivotal movement toward and away from the stack of signatures;
• said stem member having a first passage through said stem member through which air is directed to atmosphere around said apparatus;
• said stem member having a second passage in communication with said suction cup;
• a venturi tube at least partially disposed in said first passage;
• an air supply conduit connected in fluid communication with said venturi tube;
• and
• a valve connected with said air supply conduit and operable between an open condition and a closed condition, said valve being effective to enable air to flow from said venturi tube through said first passage in said stem member to atmosphere to effect generation of a vacuum which is communicated to said suction cup to induce a flow of air from said suction cup through said second passage to said first passage when said valve is in the open condition to thereby cause a portion of a signature to be gripped by said suction cup and moved relative to the stack of signatures in the hopper upon pivotal movement of said stem member away from the stack of signatures, said valve being effective to block a flow of air to said venturi tube and to said first and second passages when said valve is in the closed condition to interrupt the generation of vacuum to thereby release the grip of said suction cup on the signature.