Rotary switch with cam operated sliding contact engaging noble metal stationary contact bar surface

A rotary switch comprising:

• a base member and a housing joinable with the base member, an elongated contact bar mounted stationarily to and extending laterally of said base member, said contact bar having an exposed surface coated with a noble metal, a row of movable spring contacts each comprised of a metal strip having one end portion fastened to said base member and having an opposite deflectable free end portion extending in cantilever fashion away from said one end portion, said free end portion having an offset and having a part continuing beyond said offset and terminating in a contact tip which is spaced from said exposed surface of said stationary contact bar when said free end portion is not deflected,
• a rotor including a disk having opposite sides, an operating shaft extending from one side of the disk through said housing and the side opposite of the disk from said one side having a surface from which a plurality of concentric cam segments having a predetermined axial height project,
• said axial height of said cam segments relative to said surface being sufficient for said cam segments to press on said offsets of said spring contacts, respectively, in succession in response to rotation of said disk, with sufficient force for deflecting said free end portion to cause said contact tips to contact said exposed surface of said contact bar and subsequently slide longitudinally across said bar for said tips, respectively, to acquire a coat of noble metal from said exposed surface.

A method of coating the tips of a plurality of movable contacts with a noble metal such as silver, comprising the steps of:

• forming movable contacts of a strip of spring metal with each contact having an offset knee located between the ends of each contact and with each contact extending to and terminating in a small contact tip on one side of the knee, the tip being devoid of a noble metal coating,
• mounting on an insulating material base a contact element having a surface on which there is a layer of noble metal,
• mounting said movable contacts to said base in cantilever fashion with the tips of the movable contacts overhanging said surface of the contact element,
• providing an operating device in a housing for said switch that is operable to press on said offset knees repeatedly and cause said contact tips to deflect to make contact with and then slide along the noble metal layer on said contact element for said tips to acquire a coating of noble metal, and
• assembling the housing to said base and then operating said operating device to cause said contact tips to acquire said noble metal.