Glass membrane keyboard switch assembly for domestic appliance

• US 4,901,074 A
• Filed: 12/31/1987
• Issued: 02/13/1990
• Est. Priority Date: 12/31/1987
• Status: Expired due to Fees

• Current Assignee: Whirlpool Corporation
• Original Assignee: Whirlpool Corporation
• Inventors: Sinn, Richard E., Williams, Robert R.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Queen, Tyrone
• Application Number:
  US07/139,919
• Time in Patent Office: 775 Days
• Field of Search: 340/365 R, 340/365 S, 340/365 A, 200/5 A, 200/5 R, 200/511-512, 341/22, 341/26, 341/34, 219/10.55 B, 219/10.55 M, 219/10.57, 219/10.55 E, 219/10.55 A, 219/10.55 R, 178/17 C, 400/477, 400/479, 400/479.1
• US Class Current: 341/22
• CPC Class Codes: F24C 7/082 on ranges, e.g. control panels, illumination
• 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 13/703 characterised by spacers between contact carrying layers
• CPC Class Codes: H01H 13/785 characterised by the material of the contacts, e.g. conductive polymers
• 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 2201/028 Indium tin oxide [ITO]
• CPC Class Codes: H01H 2207/016 Jumpers; Cross-overs
• CPC Class Codes: H01H 2209/026 metallic
• CPC Class Codes: H01H 2209/038 transparent
• CPC Class Codes: H01H 2209/04 Glass
• CPC Class Codes: H01H 2209/06 transparent
• CPC Class Codes: H01H 2209/082 transparent
• CPC Class Codes: H01H 2209/084 Glass
• CPC Class Codes: H01H 2219/03 in transparent keyboard
• CPC Class Codes: H01H 2227/002 Layer thickness
• CPC Class Codes: H01H 2229/062 Maintenance or repair facilities
• CPC Class Codes: H01H 2231/012 Household appliance
• CPC Class Codes: H01H 2239/018 Ground conductor

Abstract

A keyboard switch assembly includes a thin, flexible, glass top layer forming a membrane. Disposed on an inner surface of the glass membrane is a first conductive layer forming an electrode. Disposed beneath the first conductive layer is an insulating layer or spacer having an aperture therein that defines a switch contact area. Beneath the spacer a rigid portion of the keyboard switch assembly is provided. The rigid portion of the keyboard switch assembly includes a rigid substrate with a conductive coating formed thereon to provide a second conductive layer or electrode disposed beneath the spacer. A flexible polymer layer may further be disposed between the rigid substrate and the second conductive layer to reduce point contact degradation in the keyboard switch assembly. Decorative paint layers may be formed on the inner surface of the glass membrane between the glass membrane and the first conductive layer. Alternatively, where the layers forming the keyboard switch assembly are transparent, a decorative paint layer may be disposed on an outer surface of the rigid substrate.

Claims

1. A keyboard switch assembly for a domestic appliance comprising:

a rigid substrate;

a first conductive layer disposed above said substrate;

a solid electrically insulating spacing layer disposed above said first conductive layer and having an aperture therein, said aperture defining a switch contact area;

a second conductive layer disposed above said spacing layer and spaced from said first conductive layer by said spacing layer; and

a glass top layer disposed above said second conductive layer, said glass top layer being sufficiently thin to flex causing said second conductive layer to contact said first conductive layer within said switch contact area when an area of the glass top layer located above said switch contact area is touched.

2. A keyboard switch assembly as recited in claim 1 wherein said glass top layer has a thickness of between 0.005 inch and 0.020 inch.

3. A keyboard switch assembly as recited in claim 1 wherein said glass top layer is formed of borosilicate glass.

4. A keyboard switch assembly as recited in claim 1 wherein said substrate is formed of glass of sufficient thickness to prevent damage to said glass top layer caused by excessive flexing thereof.

5. A keyboard switch assembly as recited in claim 1 wherein said first and second conductive layers are formed of indium tin oxide.

6. A keyboard switch assembly as recited in claim 1 further including a flexible polymer layer disposed between said first conductive layer and said rigid substrate to reduce point contact degradation.

7. A keyboard switch assembly as recited in claim 1 wherein said first and second conductive layers and said substrate are transparent and further including a layer of paint disposed on a side of said substrate opposite to the side of said substrate above which said first conductive layer is disposed.

8. A keyboard switch assembly as recited in claim 1 wherein said rigid substrate is formed of metal, said substrate being laminated with said other layers to prevent damage to said glass top layer caused by excessive flexing thereof.

9. A keyboard switch assembly for a domestic appliance comprising:

a rigid, transparent substrate having first and second sides;

a layer of paint disposed on said first side of said substrate;

a flexible polymer layer disposed on said second side of said substrate;

a first conductive layer disposed on said flexible polymer layer;

a solid electrically insulating spacing layer disposed above said first conductive layer and having an aperture therein, said aperture defining a switch contact area;

a second conductive layer disposed on said spacing layer and spaced from said first conductive layer by said spacing layer; and

a glass top layer disposed on said second conductive layer, said glass top layer being sufficiently thin to flex causing said second conductive layer to contact said first conductive layer within said switch contact area when an area of said glass top layer located above said switch area is touched.

10. A keyboard switch assembly as recited in claim 9 wherein said glass top layer has a thickness of between 0.005 inch and 0.020 inch.

11. A keyboard switch assembly as recited in claim 9 wherein said glass top layer is formed of borosilicate glass.

12. A keyboard switch assembly as recited in claim 9 wherein said substrate is formed of glass of sufficient thickness to prevent damage to said glass top layer caused by excessive flexing thereof.

13. A keyboard switch assembly as recited in claim 9 wherein said first and second conductive layers are formed of indium tin oxide.

14. A keyboard switch assembly for a domestic appliance comprising:

a rigid substrate;

a first conductive layer disposed on said substrate;

a solid electrically insulating spacing layer disposed above said first conductive layer and having an aperture therein, said aperture defining a switch contact area;

a second conductive layer disposed on said spacing layer and spaced from said first conductive layer by said spacing layer;

a layer of paint disposed on said second conductive layer; and

a glass top layer disposed on said paint layer, said glass top layer being sufficiently thin to flex causing said second conductive layer to contact said first conductive layer within said switch contact area when an area of said glass top layer located above said switch contact area is touched.

15. A keyboard switch assembly as recited in claim 14 wherein said glass top layer has a thickness of between 0.005 inch and 0.020 inch.

16. A keyboard switch assembly as recited in claim 14 wherein said glass top layer is formed of borosilicate glass.

17. A keyboard switch assembly as recited in claim 14 wherein said substrate is formed of glass of sufficient thickness to prevent damage to said glass top layer caused by excessive flexing thereof.

18. A keyboard switch assembly as recited in claim 14 wherein said first and second conductive layers are formed of indium tin oxide.

19. A keyboard switch assembly as recited in claim 14 wherein said rigid substrate is formed of metal, said substrate being laminated with said other layers to prevent damage to said glass top layer caused by excessive flexing thereof.

20. A keyboard switch assembly for a domestic appliance comprising:

a rigid, transparent substrate having first and second sides;

a layer of paint disposed on said first side of said substrate;

a first conductive layer disposed on said second side of said substrate;

a solid electrically insulating spacing layer disposed above said first conductive layer and having an aperture therein, said aperture defining a switch contact area;

a second conductive layer disposed on said spacing layer and spaced from said first conductive layer by said spacing layer; and

a glass top layer disposed on said second conductive layer, said glass top layer being sufficiently thin to flex causing said second conductive layer to contact said first conductive layer within said switch contact area when an area of the glass top layer located above said switch contact area is touched.

21. A keyboard switch assembly as recited in claim 20 wherein said glass top layer has a thickness of between 0.005 inch and 0.020 inch.

22. A keyboard switch assembly as recited in claim 20 wherein said glass top layer is formed of borosilicate glass.

23. A keyboard switch assembly as recited in claim 20 wherein said substrate is formed of glass of sufficient thickness to prevent damage to said glass top layer caused by excessive flexing thereof.

24. A keyboard switch assembly as recited in claim 20 wherein said first and second conductive layers are formed of indium tin oxide.