Keys for high security cylinder lock systems

A key blank for a key intended for use in cooperation with a cylinder lock having a core which is rotatable about an axis, the core of the lock including a keyway which extends inwardly from a first end of the core, the keyway having a pair of opposite sides which define a keyway cross-sectional profile when viewed in a direction transverse to the axis of rotation of the core, the core also defining a cut-out which extends to the keyway through one of the sides of the keyway in a region displaced from the first end of the core, the cylinder lock further having a plate moveably mounted within the cut-out, the plate having a cam follower projection which extends into the keyway intermediate the ends thereof, said key blank being formed from flat metal stock having first and second substantially parallel opposed side surfaces which respectively define first and second planes, said key blank comprising:

• a bow;
• a blade longitudinally extending from said bow into blade tip, said blade having first and second side faces and a pair of oppositely disposed and spaced edges which interconnect said side faces, the distance between said oppositely disposed edges being much greater than th e distance between said side faces, said first and second side faces each having longitudinally extending irregularities which in part define a blade cross-section whereby said blade may be longitudinally inserted into the keyway of the cooperating cylinder lock, said irregularities being provided in said first and second side faces by machining the opposed parallel surfaces of the flat metal stock to remove metal therefrom;
• at least one three dimensional camming projection extending outwardly from said blade first side face beyond the first of said planes, said camming projection having preselected geometric parameters and defining an axis which intersects said first plane at an angle, said camming projection being longitudinally displaced from said bow and said blade tip and being positioned between said blade edges whereby said camming projection is adapted to intercept the cut-out in the side of the keyway of the cooperating cylinder lock, the surface of said camming projection which faces said blade tip being adapted to drivingly engage the cam follower which extends into the keyway of the cooperating cylinder lock from a first side thereof whereby the cam follower projection of the moveable plate of the cooperating cylinder lock may be caused to move outwardly with respect to the keyway of the cooperating cylinder lock in response to longitudinal insertion of said blade into the lock keyway;
• and
• a three dimensional recess in said blade second side face, said recess having an axis and geometric parameters which correspond to the geometric parameters of said camming projection, said recess extending generally toward said blade first side face and being at least in partial registration with said camming projection, at least one of said geometric parameters of said recess being different from the corresponding parameter of said camming projection whereby said recess is not complementary to said camming projection.