Membrane keyboard switch assembly having selectable tactile properties

An electrical switch array comprising:

• a layer of dielectric, resilient material having a plurality of holes arranged in a pattern therein;
• a first, flexible, dielectric sheet having first and second sides and also having a plurality of dome-shaped areas therein with the convex sides of said dome-shaped areas being located on said second side and said dome-shaped areas being aligned with said holes in said layer so that said first side faces said layer;
• each said dome-shaped area being designed for snap action and also having a perimeter, with each said dome-shaped area having its perimeter aligned with respect to an associated said hole so as to be resiliently supported by a portion of said layer surrounding said hole;
• a second flexible dielectric sheet having first and second sides with said first side facing said layer;
• said first sides of said first and second sheets having first and second electrode means arranged, respectively, thereon for completing an electrical connection or makepoint represented by a said dome-shaped area when a said dome-shaped area is moved into its associated hole to enable said first electrode means to contact said second electrode means;
• a first means for supporting said array;
• and
• a second layer of resilient material positioned between said second face of said second sheet and said first supporting means;
• said layer of dielectric, resilient material and said second layer of resilient material being substantially thicker than said first and second flexible dielectric sheets, and also the thickness of said layer of dielectric resilient material and said second layer of resilient material being selected so as to affect the location of said makepoint.

An electrical switch array comprising:

• a layer of dielectric, resilient material having a plurality of holes arranged in a pattern therein;
• a first, flexible, dielectric sheet having first and second sides and also having a plurality of dome-shaped, snap-action areas therein with the convex sides of said areas being located on said second side and said areas being aligned with said holes in said layer so that said first side faces said layer;
• a second flexible dielectric sheet having first and second sides with said first side facing said layer;
• said first sides of said first and second sheets having first and second electrode means arranged, respectively, thereon for completing an electrical connection or makepoint represented by a said area when a said area is moved into its associated hole to enable said first electrode means to contact said second electrode means;
• a first plate extending over said array;
• a second layer of resilient material positioned between said second face of said second sheet and said first plate;
• a second plate having a plurality of support holes therein aligned with said holes in said layer;
• a third layer of resilient material positioned between said second plate and said second side of said first sheet;
• and
• actuable keys slidably mounted in said support holes for moving the associated dome-shaped, snap-action areas into their associated holes on said layer;
• each said dome-shaped, snap-action area having a perimeter which is supported by a portion of said layer, which said portion surrounds the associated said hole;
• said layer, said second layer and said third layer being made of flexible foam such as urethane and said first and second sheets being made of a plastic such as Mylar;
• said layer, said second layer, and said third layer each having a thickness which ranges from approximately 0.10 to 0.50 inch, and said first and second sheets each having a thickness of approximately 0.004 to 0.050 inch when said first and second sheets are made of a plastic like Mylar, and said first and second sheets each having a thickness of approximately 0.050 to 0.20 inch when said first and second sheets are made of silicone rubber.