Membrane switch with sequentially closable contacts

A switch of the type having an insulating substrate, a plurality of metallized switch contacts on one surface of the substrate, the switch contacts being adjacent to each other, a flexible sheet extending parallel to, and spaced from the one surface of said substrate, the sheet having an opposed surface which is opposed to the one surface and having a commoning conductor on the opposed surface so that upon flexure of the sheet towards the one surface and engagement of the commoning conductor with the switch contacts, the switch contacts are electrically commoned, the switch being characterized in that:

• the one surface of the substrate has first, second, and third switch contacts thereon,
• the flexible sheet has first and second contact projections extending from the opposed surface towards the one surface of the substrate, the first contact projection being against, and in electrical contact with, the first switch contact, the second contact projection being spaced from, and in opposed relationship to, the second switch contact,
• the flexible sheet has a pair of supporting projections extending from the opposed surface thereof, the supporting projections having apices which are against the one surface of the substrate at locations spaced from the first, second, and third switch contacts, the flexible sheet being an insulating film, the commoning conductor comprising metallization on the opposed surface of the film whereby,
• upon application of a switch closing force to the flexible sheet at a location opposed to, and in alignment with, the third switch contact, the portion of the commoning conductor on the second contact projection is moved against the second switch contact, and thereafter the portion of the commoning conductor which is opposed to the third switch contact is thereafter moved against the third switch contact.