Sheet membrane keyboard and electronic apparatus using same

• US 4,736,190 A
• Filed: 10/07/1985
• Issued: 04/05/1988
• Est. Priority Date: 11/01/1982
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Fiorella, Charles M.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Fatahi-Yar, Mahmoud
• Application Number:
  US06/784,720
• Time in Patent Office: 911 Days
• Field of Search: 340/365 C, 340/365 A, 340/365 R, 200/5 A, 200/159 B, 200/160, 364/700, 364/705, 364/707, 364/709, 178/18, 400/477, 400/485
• US Class Current: 341/22
• CPC Class Codes: G06F 15/0216 Constructional details or arrangements
• 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 2203/02 Interspersed fingers
• CPC Class Codes: H01H 2203/03 printed on casing
• CPC Class Codes: H01H 2207/002 Conductive rubber; Zebra
• CPC Class Codes: H01H 2207/004 Printed circuit tail
• CPC Class Codes: H01H 2207/008 Adhesive means; Conductive adhesive
• CPC Class Codes: H01H 2207/016 Jumpers; Cross-overs
• CPC Class Codes: H01H 2209/074 elastomeric
• CPC Class Codes: H01H 2211/028 Contacts in depressions of layers
• CPC Class Codes: H01H 2215/008 Part of substrate or membrane
• CPC Class Codes: H01H 2219/01 Liquid crystal
• CPC Class Codes: H01H 2223/022 Adhesive
• CPC Class Codes: H01H 2229/004 Conductive ink
• CPC Class Codes: H01H 2229/006 Pad transfer printing
• CPC Class Codes: H01H 2229/018 Testing
• CPC Class Codes: H01H 2229/034 Positioning of layers
• CPC Class Codes: H01H 2231/002 Calculator, computer
• CPC Class Codes: H01H 2239/01 combined with other elements on the same substrate
• CPC Class Codes: H05K 1/0284 : Details of three-dimensional rigid printed circuit boards H05K1/119 takes precedence; shaping of the substrate H05K3/0014
• CPC Class Codes: H05K 1/056 : the metal substrate being covered by an organic insulating layer
• CPC Class Codes: H05K 1/095 : for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: H05K 1/144 : Stacked arrangements of planar printed circuit boards
• CPC Class Codes: H05K 1/182 : associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
• CPC Class Codes: H05K 2201/09036 : Recesses or grooves in insulating substrate recess in metallic substrate H05K2201/09745
• CPC Class Codes: H05K 2201/0999 : Circuit printed on or in housing, e.g. housing as PCB; Circuit printed on the case of a component; PCB affixed to housing
• CPC Class Codes: H05K 2201/10037 : Printed or non-printed battery
• CPC Class Codes: H05K 2201/10053 : Switch
• CPC Class Codes: H05K 2201/10128 : Display
• CPC Class Codes: H05K 2201/10689 : Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• CPC Class Codes: H05K 3/321 : by conductive adhesives
• CPC Class Codes: H05K 3/325 : by abutting or pinching, i.e. without alloying process; mechanical auxiliary parts therefor adaptations of leads inserted in holes for press-fit connections H05K3/308
• CPC Class Codes: H05K 3/368 : parallel to each other H05K3/361 takes precedence
• CPC Class Codes: H05K 3/4664 : Adding a circuit layer by thick film methods, e.g. printing techniques or by other techniques for making conductive patterns by using pastes, inks or powders H05K3/4647 takes precedence

Abstract

The present invention is a simplified membrane keyboard employing a single flexible sheet. This membrane keyboard is employed in an electronic apparatus having an external case with a nonconducting keyboard surface. This nonconducting keyboard surface has a plurality of depressions corresponding to key switch positions. The keyboard surface is covered by a keyboard sheet. This keyboard sheet has a flexible membrane with opposed first and second surfaces, the first surface disposed adjacent to and substantially covering the keyboard surface of the external case. An interconnection pattern is placed upon the first surface of the flexible membrane. This interconnection pattern has a plurality of conductors and most particularly has a pair of conductors in proximity at each key switch position. Pressure applied to the second surface of the flexible membrane causes the flexible membrane to flex until the two conductors contact a conductive layer disposed in the bottom of the corresponding depression. This contact causes electrical conduction between the two conductors, thereby giving rise to a closed key operation. In a preferred embodiment graphic matter identifying the key areas of the flexible sheet, that is those areas overlying the depressions, is applied to the second surface of the flexible sheet. This invention is adapted for use in calculators, electronic learning aids, electronic games, small computer systems and other electronic apparatuses which employ keyboards.

Claims

1. A keyboard structure for an electronic apparatus comprising:

a body of non-conductive material providing a keyboard surface;

said body of non-conductive material having a plurality of spaced depressions formed therein to extend partially through the thickness thereof, said spaced depressions opening onto said keyboard surface and respectively located at corresponding key switch positions;

an electrically conductive layer disposed at the bottom of each of said depressions within said body of non-conductive material;

a keyboard sheet including a flexible membrane of non-conductive material having opposing first and second surfaces, said first surface being disposed adjacent to and substantially covering said keyboard surface;

an interconnection pattern including a plurality of electrical conductors disposed on said first surface of said flexible membrane facing said keyboard surface and arranged to provide a pair of electrical conductors in proximity at each of said key switch positions; and

said flexible membrane flexing in a direction toward said keyboard surface of said body to move a respective pair of electrical conductors corresponding to a particular key switch position into engagement with said conductive layer disposed at the bottom of the depression located at the respective key switch position in response to pressure on said second surface of said flexible membrane selectively applied at said particular key switch position, whereby an electrical connection occurs between said respective pair of conductors via said conductive layer at the selected key switch position.

2. A keyboard structure as set forth in claim 1, wherein said interconnection pattern has a first set of electrical conductors in which the respective pairs of electrical conductors in proximity at each of said key switch positions are incorporated, said first set of electrical conductors being arranged to provide at least one crossover conductor group comprising a pair of conductors disposed on opposite sides of and transverse to another conductor interposed therebetween and in spaced relation thereto to define a crossover location.

a pattern of insulating material overlying said first set of electrical conductors and including respective small insulators disposed on said first set of electrical conductors at each of said crossover locations, each said small insulator being positioned over said another conductor and extending between said pair of conductors disposed on opposite sides thereof of the respective crossover conductor group, and

a second set of electrical conductors including respective electrical conductors disposed on said pattern of insulating material at each of said crossover locations, each said electrical conductor of said second set of electrical conductors being positioned over a small insulator and electrically connecting said pair of conductors of a respective crossover conductor group while being electrically insulated from said another conductor by said small insulator at the corresponding crossover location.

3. An electronic apparatus comprising:

an exterior case adapted to contain electronic components and having a body portion of non-conductive material providing a keyboard surface outwardly disposed with respect to the interior of said case;

said body portion of non-conductive material having a plurality of spaced depressions formed therein to extend partially through the thickness thereof, said spaced depressions opening onto said keyboard surface and respectively located at corresponding key switch positions;

an electrically conductive layer disposed at the bottom of each of said depressions within said body portion of non-conductive material;

a keyboard sheet including a flexible membrane of non-conductive material having opposing first and second surfaces, said first surface being disposed adjacent to and substantially covering said keyboard surface;

an interconnection pattern including a plurality of electrical conductors disposed on said first surface of said flexible membrane facing said keyboard surface and arranged to provide a pair of electrical conductors in proximity at each of said key switch positions;

said flexible membrane flexing in a direction toward said keyboard surface of said exterior case to move a respective pair of electrical conductors corresponding to a particular key switch position into engagement with said conductive layer disposed at the bottom of the depression located at the respective key switch position in response to pressure on said second surface of said flexible membrane selectively applied at said particular key switch position, whereby an electrical connection occurs between said respective pair of conductors via said conductive layer at the selected key switch position; and

electronic circuit means disposed in said exterior case and connected to said interconnection pattern, said electronic circuit means including

means for sensing an electrical connection between respective pairs of conductors at each of said key switch positions, and

means for performing an electronic function and generating a result in response to sensed electrical connections between pairs of conductors corresponding to particular key switch positions.

4. An electronic apparatus as set forth in claim 3, wherein said interconnection pattern has a first set of electrical conductors in which the respective pairs of electrical conductors in proximity at each of said key switch positions are incorporated, said first set of electrical conductors being arranged to provide at least one crossover conductor group comprising a pair of conductors disposed on opposite sides of and transverse to another conductor interposed therebetween and in spaced relation thereto to define a crossover location.

a pattern of insulating material overlying said first set of electrical conductors and including respective small insulators disposed on said first set of electrical conductors at each of said crossover locations, each said small insulator being positioned over said another conductor and extending between said pair of conductors disposed on opposite sides thereof of the respective crossover conductor group, and

a second set of electrical conductors including respective electrical conductors disposed on said pattern of insulating material at each of said crossover locations, each said electrical conductor of said second set of electrical conductors being positioned over a small insulator and electrically connecting said pair of conductors of a respective crossover conductor group while being electrically insulated from said another conductor by said small insulator at the corresponding crossover location.

5. In an electronic apparatus, a keyboard structure comprising:

an exterior case for the electronic apparatus adapted to contain electronic components thereof and having a body portion on non-conductive material providing a keyboard surface outwardly disposed with respect to the interior of said case;

said body portion of non-conductive material having a plurality of spaced depressions formed therein to extend partially through the thickness thereof, said spaced depressions opening onto said keyboard surface and respectively located at corresponding key switch positions;

an electrically conductive layer disposed at the bottom of each of said depressions within said body portion of non-conductive material;

a keyboard sheet including a flexible membrane of non-conductive material having opposing first and second surfaces, said first surface being disposed adjacent to and substantially covering said keyboard surface;

an interconnection pattern including a plurality of electrical conductors disposed on said first surface of said flexible membrane facing said keyboard surface and arranged to prvide a pair of electrical conductors in proximity at each of said key switch positions; and

said flexible membrane flexing in a direction toward said keyboard surface of said exterior case to move a respective pair of electrical conductors corresponding to a particular key switch position into engagement with said conductive layer disposed at the bottom of the depression located at the respective key switch position in response to pressure on said second surface of said flexible membrane selectively applied at said particular key switch position, whereby an electrical connection occurs between said respective pair of conductors via said conductive layer at the selected key switch position.

6. In an electronic apparatus, a keyboard structure as set forth in claim 5 wherein said interconnection pattern has a first set of electrical conductors in which the respective pairs of electrical conductors in proximity at each of said key switch positions are incorporated, said first set of electrical conductors being arranged to provide at least one crossover conductor group comprising a pair of conductors disposed on opposite sides of and transverse to another conductor interposed therebetween and in spaced relation thereto to define a crossover location.

a pattern of insulating material overlying said first set of electrical conductors and including respective small insulators disposed on said first set of electrical conductors at each of said crossover locations, each said small insulator being positioned over said another conductor and extending between said pair of conductors disposed on opposite sides thereof of the respective crossover conductor group, and

a second set of electrical conductors including respective electrical conductors disposed on said pattern of insulating material at each of said crossover locations, each said electrical conductor of said second set of electrical conductors being positioned over a small insulator and electrically connecting said pair of conductors of a respective crossover conductor group while being electrically insulated from said another conductor, by said small insulator at the corresponding crossover location.