Calculator keyboard switch with disc spring contact and printed circuit board

Abstract

A keyboard switch assembly including a printed circuit board having four switch terminals on one side of the board, three of the terminals being arranged in a triangle and the fourth disposed within the triangle. Conductors on the one side of the board are respectively joined to the interior terminal and at least one of the three terminals. A conductive, generally triangular, snap-acting dome switch member is provided having arcuate apices, projections being respectively formed from the apices and respectively engaging the three terminals thereby spacing the periphery of the switch element from the one surface of the printed circuit board and the conductors thereon, at least the conductor connected to the interior terminal extending under the dome. The switch element has a fourth projection formed from the interior of the dome adjacent the center thereof which is in registry with the interior terminal and engages that terminal when the dome is deflected thereby completing an electrical circuit between the three terminals and the interior terminal. A layer of insulating material covers the conductors exclusive of the terminals. A sheet of insulating material covers the insulating layer and has an opening therein which receives and locates the switch member. Another sheet of insulating material covers the first sheet and the switch member. A plate covers the second insulating sheet and has an opening therein which receives a push button in registry with the switch element, depression of the push button actuating the dome of the switch member to a non-overcenter, deflected position in which the interior projection on the dome engages the interior switch terminal.

What is claimed is: .Badd..[. 
     
       1.  In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said .[.bush.]. .Iadd.push .Iaddend.button, the improvement comprising an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, said switch element being positioned in facing relationship with said one surface and said conductors, said switch element having first and second spaced contact areas thereon, said first contact area engaging said first terminal portion, said second contact area being in registry with said second terminal portion and engaging the same when said element is in said deflected position thereby electrically connecting said first and second terminal portions, and means for holding said push button, switch member and board in operative relationship..]. 2. The assembly of claim .Badd..[.1.]..Baddend. .Iadd.23 .Iaddend.further comprising a layer of insulating material covering said conductors excluding said terminal portions. .Badd..[.3. The assembly of claim 2 wherein said element is a snap-acting dome, said second contact area being at the center of said dome, said one surface of said board having a third conductor thereon at least partially surrounding said second terminal portion, closely spaced therefrom and generally coplanar therewith, the area of said dome surrounding said second contact area engaging the insulation covering said third conductor upon further deflection of said dome following engagement of said second contact area with said second terminal portion thereby to protect said second contact area..]..Baddend. 4. .[.The assembly of claim 1 wherein.]. .Iadd.In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said push button, .Iadd..[..[.the improvement comprising.]..]..Iaddend. .Iadd.an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, .Iaddend..Badd.the improvement wherein .Baddend..Iadd.said switch element .Iaddend..Iadd..[..[.being.]..]..Iaddend. .Badd.is a snap-acting dome .Baddend..Iadd.positioned in facing relationship with said one surface and said conductors, said .Iadd..[..[.switch element.]..]..Iaddend. .Badd.dome .Baddend..Iadd.having .Iaddend..Badd.a .Baddend..Iadd.first .Iadd..[..[.and second spaced.]..]..Iaddend. contact .Iadd..[..[.areas.]..]..Iaddend. .Badd.area .Baddend..Iadd..[..[.thereon.]..]..Iaddend. .Badd.adjacent its periphery and a second contact area adjacent its center, .Baddend..Iadd.said first contact area engaging said first terminal portion .Iaddend..Badd.in both positions of said dome, .Baddend..Iadd.said second contact area being in registry with said second terminal portion and engaging the same when said .Iaddend..Iadd..[..[.element.]..]..Iaddend. .Badd.dome .Baddend..Iadd.is in said deflected position thereby electrically connecting said first and second terminal portions, and means for holding said push button, .Iaddend..Iadd. .[..[.switch member.]..]..Iaddend. .Badd.dome .Baddend..Iadd.and board in operative relationship, .Iaddend.said one surface of said board .[.has.]. .Iadd.having .Iaddend.at least a third conductor thereon intermediate and spaced from said first and second conductors and generally coplanar therewith, said third conductor extending .Iadd.between said terminal .Iadd..[..[.portion.]..]..Iaddend. .Badd.portions .Baddend..Iadd.and .Iaddend.under said .[..[.element.]..]. .Badd.dome .Baddend.from a location on said one surface remote therefrom, .Iadd..[..[.means for maintaining .Iaddend.said element in .[.its deflected position being spaced from.]. .Iadd.spaced relationship with.]..]..Iaddend. .Badd.said first contact area being a projection on said dome adjacent the periphery thereof spacing said dome from .Baddend.said third conductor .[.,.]. .Iadd.in both positions of said .Iadd..[..[.element.]..]..Iaddend. .Badd.dome .Baddend..Iadd.whereby .Iaddend.there .[.being.].  .Iadd.is .Iaddend.no electrical connection between said third conductor and said .[..[.element.]..]. .Badd.dome .Baddend.in either position thereof. .Badd..[..[.5. The assembly of claim 4 wherein said element is a snap-acting dome, said second contact area being at the center of said dome .[., said third conductor being intermediate said first and second terminal portions and generally coplanar therewith.]...]..]. 6. .[.The assembly of claim 1 wherein.]. .Iadd.In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said push button, the improvement comprising an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, said switch element being positioned in facing relationship with said one surface and said conductors, said switch element having first and second spaced contact areas thereon, said first contact area engaging said first terminal portion, said second contact area being in registry with said second terminal portion and engaging the same when said element is in said deflected position thereby electrically connecting said first and second terminal portions, and means for holding said push button, switch member and board in operative relationship, .Iaddend.said one surface of said board has a third conductor thereon at least partially surrounding said second terminal portion, spaced therefrom and generally coplanar therewith, the area of said element surrounding said second contact area engaging said third conductor upon further deflection of said element following engagement of said second contact with said second terminal portion thereby to protect said element and second contact area.  7. The assembly of claim .Badd..[.1.]..Baddend. .Iadd.23 .Iaddend.wherein a section of at least said second conductor extends under said .[.element.]. .Iadd..[..[.device.]..]..Iaddend. .Badd.dome .Baddend.from a location on said one surface remote therefrom. .Badd..[..[.8. The assembly of claim .Badd..[.1.]..Baddend. .Iadd.23 .Iaddend.wherein said .[.element.]. .Iadd.device .Iaddend.is a snap-acting dome, said second contact area being at the center of said dome..]..]. 9. The assembly of claim .Badd..[..[.8.]..]..Baddend. 23  wherein said second contact area comprises a projection on the interior of said dome. .Badd.10. .[.The assembly of claim 8.]. .Iadd.In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said push button, the improvement comprising an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, said switch element being positioned in facing relationship with said one surface and said conductors, said switch element having first and second spaced contact areas thereon, said first contact area engaging said first terminal portion, said second contact area being in registry with said second terminal portion and engaging the same when said element is in said deflected positon thereby electrically connecting said first and second terminal portions, and means for holding said push button, switch member and board in operative relationship, wherein said element is a snap-acting dome, said second contact area being at the center of said dome, .Iaddend.further comprising third, fourth and fifth switch terminals on said one surface of said board, said third through fifth terminals and said first terminal portion being arranged in a rectangle with said second terminal portion in the interior thereof, said first contact area comprising a first projection formed from said dome adjacent the periphery thereof, said dome having second, third and fourth projections formed therefrom adjacent the periphery thereof and respectively engaging said third, fourth and fifth switch terminals, said projections spacing the periphery of said dome from said one surface of said board and said conductor, said second contact area comprising a fifth projection formed from the interior of said dome. 11. The assembly of claim 10 wherein said switch element is generally rectangular with arcuate corners coaxial with the center of said dome, said first through fourth projections being formed from said corners. 12. .[.The assembly of claim 8 wherein.]. .Iadd.In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said push button, the improvement comprising an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, said switch element being positioned in facing relationship with said one surface and said conductors, said switch element having first and second spaced contact areas thereon, said first contact area engaging said first terminal portion, said second contact area being in registry with said second terminal portion and engaging the same when said element is in said deflected position thereby electrically connecting said first and second terminal portions, and means for holding said push button, switch member and board in operative relationship, wherein said element is a snap-acting dome, said second contact area being at the center of said dome, .Iaddend.said first contact area .[.comprises.]. .Iadd.comprising .Iaddend.a projection on said switch element spacing the periphery of said dome from said surface of said board and said conductors. 13. The assembly of claim 12 wherein said projection is formed from said dome adjacent the periphery thereof. 14. The assembly of claim 13 wherein said switch member includes a flat portion joined to the periphery of said dome, said projection being formed from said flat portion. 15. .[.The assembly of claim 8.]. .Iadd.In a keyboard switch assembly including a push button manually actuable from an inactive to a switch-actuating position, and a conductive switch member including a resilient element actuated by said push button from a normal to a deflected position and resiliently returning to its normal position upon removal of force from said push button, the improvement comprising an insulative board having opposite surfaces, one only of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, said switch element being positioned in facing relationship with said one surface and said conductors, said switch element having first and second spaced contact areas thereon, said first contact area engaging said first terminal portion, said second contact area being in registry with said second terminal portion and engaging the same when said element is in said deflected position thereby electrically connecting said first and second terminal portions, and means for holding said push button, switch member and board in operative relationship, wherein said element is a snap-acting dome, said second contact area being at the center of said dome and .Iaddend.further comprising third and fourth switch terminals on said one surface of said board, said third and fourth terminals and said first terminal portion being arranged in a triangle with said second terminal portion in the interior thereof, said first contact area comprising a first projection formed from said dome adjacent the periphery thereof, said dome having second and third projections formed therefrom adjacent the periphery thereof and respectively engaging said third and fourth switch terminals, said projections spacing the periphery of said dome from said one surface of said board and said conductors, said second contact area comprising a fourth projection formed from the interior of said dome. 16. The assembly of claim 15 wherein said switch element is generally triangular with arcuate apices coaxial with the center of said dome, said first, second and third projections being formed from said apices. 17. The assembly of claim 16 wherein said holding means comprises a layer of insulating material covering said conductors excluding said terminal portions and terminals, a first sheet of insulating material covering said layer and having an opening therein receiving said switch element and conforming thereto for locating the same, a second sheet of insulating material covering said first sheet and switch element, and a plate member covering said second sheet and having an opening therein receiving said push button, said push button acting on said dome through said second sheet. 18. The assembly of claim 16 wherein a section of at least said second conductor extends under said dome from a location on said one surface remote therefrom, said one surface of said board having a third conductor thereon at least partially surrounding said second terminal portion, spaced thereof and generally coplanar therewith, said conductors exclusive of said terminal portions having a layer of insulating material thereon, the area of said dome surrounding said fourth projection engaging the insulation covering said third conductor upon further deflection of said dome following engagement of said second contact area with said second terminal portion thereby to protect said fourth projection. 19. The assembly of claim 18 wherein said third conductor completely surrounds said second terminal portion and is joined to said second conductor. 20. The assembly of claim 18 wherein said third conductor partially surrounds said second terminal portion and is joined to a fourth conductor on said one surface of said board which extends under said dome. 21. The assembly of claim 18 wherein said first conductor is joined to at least said .[.second.]. .Iadd.third .Iaddend.terminal. 22. The assembly of claim 18 wherein said board has a fourth conductor thereon which extends under said dome. .Iadd. 23. In a keyboard switch assembly including a resilient, conductive switch device manually actuable from a normal to a deflected position, said switch device resiliently returning to its normal position upon removal of force therefrom, .Iaddend..Iadd..[..[.the improvement comprising.]..]..Iaddend. .Badd.and .Baddend..Iadd.an insulative member having opposite surfaces, one of said surfaces having first and second elongated conductors thereon, said first conductor including a first switch terminal portion and said second conductor including a second switch terminal portion, said conductors and terminal portions being generally coplanar, .Iaddend..Badd.the improvement wherein .Baddend..Iadd.said switch device .Iaddend..Iadd..[..[.being.]..]..Iaddend. .Badd.is a snap-acting dome .Baddend..Iadd.positioned in facing relationship with said one surface and said conductors, said .Iaddend..Iadd..[..[.switch device.]..]..Iaddend. .Badd.dome .Baddend..Iadd.having .Iaddend..Badd.a .Baddend..Iadd.first .Iaddend..Badd.contact area adjacent its periphery and .Baddend..Badd.a .Baddend..Iadd.second .Iaddend..Iadd..[..[.spaced.]..]..Iaddend. .Iadd.contact .Iaddend..Iadd..[..[.areas.]..]..Iaddend..Badd.area .Baddend..Iadd..[..[.thereon.]..]..Iaddend. .Badd.adjacent its center, .Baddend..Iadd.said contact areas being respectively in registry with said terminal portions.Iaddend..Iadd..[..[.and.]..]..Iaddend..Badd., said first contact area .Baddend..Iadd.engaging .Iaddend. .Iadd..[..[.the same.]..]..Iaddend. .Badd.said first terminal portion in both positions of said dome, said second contact area engaging said second terminal portion .Baddend..Iadd.when said .Iaddend..Iadd..[..[.device.]..]..Iaddend. .Badd.dome .Baddend..Iadd.is in said deflected position thereby electrically connecting said terminal portions, .Iaddend..Iadd..[..[.at least one of.]..]..Iaddend. .Iadd.said .Iaddend..Badd.second .Baddend..Iadd.contact .Iaddend..Iadd..[..[.areas.]..]..Iaddend..Badd.area .Baddend..Iadd.being spaced from .Iaddend..Iadd..[..[.the respective.]..]..Iaddend. .Badd.said second .Baddend..Iadd.terminal portion in said normal position of said device, said one surface of said member having at least a third conductor thereon intermediate and spaced from said first and second conductors and generally coplanar therewith, said third conductor extending between said .Iaddend..Iadd..[..[.contact areas.]..]..Iaddend. .Badd.terminal portions .Baddend..Iadd.and under said .Iaddend..Iadd..[..[.device.]..]..Iaddend. .Badd.dome .Baddend..Iadd.from a location on said one surface remote therefrom, .Iaddend..Iadd..[..[.means for maintaining said device in spaced relationship with.]..]..Iaddend. .Badd.said first contact area being a projection on said dome adjacent the periphery thereof spacing said dome from .Baddend..Iadd.said third conductor in both positions of said .Iaddend..Iadd..[..[.device.]..]. .Iaddend..Badd.dome .Baddend..Iadd.whereby there is no electrical connection between said third conductor and said .Iaddend..Iadd..[..[.device.]..]..Iaddend. .Badd.dome .Baddend..Iadd.in either position thereof, and means for holding said .Iaddend..Iadd..[..[.switch device.]..]..Iaddend. .Badd.dome .Baddend..Iadd.and insulative member in operative relationship. .Iaddend. .Iadd. 24. The assembly of claim .Iaddend..Iadd..[..[.8.]..]..Iaddend. 23 .Iadd.further comprising third and fourth switch terminals on said one surface of said member, said third and fourth terminals and said first terminal portion being arranged in a triangle with said second terminal portion in the interior thereof, .Iaddend..Iadd..[..[.said first contact area comprising a first projection formed from said dome adjacent the periphery thereof.]..]..Iaddend. .Iadd.said dome having second and third projections formed .Iaddend..Iadd..[..[.therefrom.]..]..Iaddend. .Badd.thereon .Baddend..Iadd.adjacent the periphery thereof and respectively engaging said third and fourth switch terminals, said projections spacing the periphery of said dome from said one surface of said board and said conductors, said second contact area comprising a fourth projection formed from the interior of said dome.Iaddend..Iadd..[..[., said maintaining means comprising said first, second and third projections.]..]..Iaddend.. .Iadd. 25. The assembly of claim 24 wherein said switch device is generally triangular with arcuate apices coaxial with the center of said dome, said first, second and third projections being formed from said apices. .Iaddend..Iadd. 26. The assembly of claim 2 wherein .Iadd..[..[.said device is a snap-acting dome, said first contact area engaging said first terminal portion in both positions of said device, said second contact area being at the center of said dome and being spaced from said second contact area in said normal position of said device,.]..]..Iaddend. .Iadd.said one surface of said member .Iaddend..Iadd..[..[.having.]..]..Iaddend. .Badd.has .Baddend..Iadd.a fourth conductor thereon spaced from said third conductor and first terminal portion and at least partially surrounding said second terminal portion, closely spaced therefrom and generally coplanar therewith, the area of said dome surrounding said second contact area engaging the insulation covering said fourth conductor upon further deflection of said dome following engagement of said second contact area with said second terminal portion thereby to protect said second contact area. .Iaddend..Badd. 27. The assembly of claim 12 wherein a section of at least said second conductor extends under said dome from a location on said one surface remote therefrom. .Baddend.