Membrane keyboard switch assembly having selectable tactile properties

• US 4,362,911 A
• Filed: 09/17/1980
• Issued: 12/07/1982
• Est. Priority Date: 09/17/1980
• Status: Expired due to Term

• Current Assignee: NCR Corporation
• Original Assignee: NCR Corporation
• Inventors: Gross, Jack R., Sears, Ronald J.
• Primary Examiner(s): Scott, J. R.
• Application Number:
  US06/187,904
• Time in Patent Office: 811 Days
• Field of Search: 200/1, 200/5 R, 200/5 A, 200/85, 200/86 R, 200/159 B
• US Class Current: 200/5.00A
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 13/80 characterised by the manner of cooperation of the contacts, e.g. with both contacts movable or with bounceless contacts
• CPC Class Codes: H01H 2201/008 Both contacts movable
• CPC Class Codes: H01H 2209/014 composed of different layers; Lubricant in between
• CPC Class Codes: H01H 2215/002 Longer travel
• CPC Class Codes: H01H 2215/008 Part of substrate or membrane
• CPC Class Codes: H01H 2217/02 After travel
• CPC Class Codes: H01H 2221/042 Foam
• CPC Class Codes: H01H 2227/002 Layer thickness
• CPC Class Codes: H01H 2229/018 Testing
• CPC Class Codes: H01H 2229/042 Snap coupling; Snap mounting

Abstract

A "membrane"-type keyboard includes a resilient foam layer having an array of holes therein with the layer being sandwiched between first and second flexible membranes having electrical conductors thereon which are arranged to complete a circuit associated with a hole when the first and second membranes are moved toward each other. Embodiments including dome-shaped areas in the first flexible membranes provide for "tactile feedback" and additional foam layers enhance the operating characteristics of the embodiments. The method generally entails determining the operating parameters of a desired keyboard and simply changing the relative density and/or thicknesses of various layers and flexible membranes in the keyboard to obtain radically variable paremeters, as for example, the location of the "makepoint" of the switch at various positions between the start and end of "key travel."

Claims

1. 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; and

a second dielectric member having first and second sides with said first side facing said layer;

said first sides of said first sheet and second member having first and second electrode means arranged, respectively, thereon for completing an electrical connection 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;

said layer of dielectric resilient material being made of flexile foam, such as urethane, and said first dielectric sheet being made of plastic material;

each said dome-shaped area having a size to enable it to be depressed by a user'"'"'s finger; and

said layer of dielectric resilient material being substantially thicker than said first dielectric sheet;

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.

2. 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.

3. The array as claimed in claim 2 further comprising:

a second means having support holes therein which are aligned with said holes in said layer;

a third layer of resilient material positioned between said second means and said second side of said first sheet; and

actuable keys slidably mounted in said support holes for engaging said third layer and also for moving the associated dome-shaped areas into their associated holes in said layer.

4. The array as claimed in claim 3 in which each of said actuable keys has a length of travel beginning with a start point and ending with an end point, with said makepoint or electrical connection occurring therebetween;

said layer, second layer, and third layer having thicknesses which are selected to locate said makepoint at various positions between said start and end points.

5. The array as claimed in claim 4 in which said layer, second layer and third layer are substantially equal in thickness.

6. 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.

7. The array as claimed in claim 6 in which said third layer has a plurality of concave areas therein arranged in a pattern so that a said concave area contacts an associated dome-shaped snap-action area in said first sheet.