Keyboard switch assembly having flexible contact carrying member between contact carrying substrate and flexible, resilient, key-depressible bubble protrusions

A switch assembly comprising:

• a planar substrate having a conductive circuit pattern printed on a surface thereof, the circuit pattern defining a plurality of sets of switch contacts each set including at least two separate contacts;
• a planar dielectric spacer disposed adjacent the surface of the substrate and having a different aperture therethrough at each of the sets of switch contacts;
• a thin planar contact carrying dielectric member disposed adjacent the spacer opposite the spacer from the substrate and having a conductive circuit pattern printed on a surface thereof facing the spacer and the substrate to close a set of switch contacts on the substrate upon being forced through an aperture in the spacer and into engagement therewith;
• a thin layer of flexible material having a planar portion disposed adjacent the contact carrying member opposite the spacer and having a different protrusion therein adjacent each of the different apertures in the spacer, each of the protrusions being a continuation of the layer and extending outwardly from the layer on the opposite side of the layer from the spacer;
• and
• an actuator mechanism including a spring biased key, a follower, and a follower spring providing the sole coupling between the key and follower positioned adjacent each protrusion, the follower engaging the adjacent protrusion with a force that increases in response to actuation of the key by an operator to force said protrusion into engagement with the dielectric member to force the conductive circuit pattern thereon into contact closure engagement with a set of switch contacts, the follower spring limiting the force that can be applied through the follower to the protrusion even though a greater force may be applied to the key.