Keyboard with removable modular keys

A keyboard comprising a support plate having an external surface and an internal surface and provided with a plurality of through openings each having two pairs of longer edges;

• a printed circuit board connected to said support plate;
• means for maintaining said printed circuit board parallel to and beneath said support plate at a determined small distance therefrom;
• an electrical circuit carried on a first surface of said printed circuit board facing the internal surface of said support plate and having a plurality of pairs of conductors disposed in correspondence with said plurality of through openings;
• and a plurality of modular keys, each one of said modular keys comprising:
• a central body insertable into each one of said through openings and having transverse shoulders and a lower portion including four lower pins projecting downwardly and disposed in a cruciform configuration parallel to diagonals of the two pairs of edges of one through opening upon insertion of said central body into said one through openings, a lower hollow cavity having an axial hole, longitudinal guide means and a stop element;
• an insulated dome-shaped spring mounted in said lower hollow cavity and including a dome portion having a base portion and four anchor arms projecting from and coplanar with said base portion, wherein said four anchor arms are disposed in a cruciform configuration, and each arm defines on its free end a projecting portion provided with a longitudinal cavity, and wherein each of said four lower pins is insertable into the longitudinal cavity of the projecting portion of each arm of said dome-shaped spring:
• contact means carried by the dome portion of said dome-shaped spring and actuatable for contacting a corresponding pair of conductors of said electrical circuit;
• an actuator member guided by said longitudinal guide means along a central longitudinal axis for actuating said contact means;
• a striker interposed between said actuator member and said dome-shaped spring;
• a central coil spring disposed between said striker and said actuator member;
• and
• mounting means for removably mounting said central body in each one of said through openings of said support plate, said mounting means comprising two longitudinal and resilient tongues disposed at opposite sides with respect to said central longitudinal axis and provided with tooth portions cooperable with the internal surface of said first support plate upon cooperation of said transverse shoulders with the external surface of said support plate;
• wherein said anchor arms and said base portion of the dome-shaped spring bear on said printed circuit board upon the insertion of said central body in said through opening;
• wherein said dome-shaped spring is removable together with said central body through said opening;
• and
• wherein said printed circuit board is subjected only to the pressure of said spring means and said dome portion when said actuator member is arrested by said stop, while any further pressure of said actuator member on said stop element is absorbed by said support plate through said transverse shoulders.