Multi-contact push-button switch and plural embodiment for keyboard switch assembly

Claim 1

A pushbutton switch including a flat spring plate having a switch position comprising: a pre-stressed domed portion extending upwardly from said flat spring plate and having a central portion and a plurality of radial webs connecting said central portion and said flat spring plate, said flat spring plate surrounding said domed portion, said flat spring plate integral with the outer ends of said radial webs to constrain said webs radially and circumferentially; an upwardly bent portion at the junction between each web and said flat spring plate, said bent portion constraining said webs to deflect radially inward of said bent portion; a plurality of cantilevered spring contact members extending from said centre portion, a contact member between at least one adjacent pair of radial webs and extending a radial distance less than said radial webs, said contact member extending downward from said domed portion toward the plane of said flat spring plate; a contact area at the radially outward end of each contact member; a circuit member positioned below and spaced from said flat spring plate and including contact areas beneath said contact areas of said spring contact members; a pushbutton mounted above said flat spring plate, over said domed portion to apply a downward force thereto, to deflect said domed portion; said domed portion, on application of said downward force, arranged to snap downward toward said circuit member, said domed portion constrained by said upwardly bent portion to return said domed portion to an undeflected position.