Mechanical bistable device

Claim 1

A snap acting operator comprising: a housing having a recess therein; a movable member; motion direction means to guide movement of said member, said member having a recess therein, said member recess extending toward and reaching a first apex pointing in a first predetermined direction, said housing recess extending toward and reaching a second apex pointing in a second predetermined direction opposite said first predetermined direction, said housing recess having a projection fixed relative thereto on each of two opposite sides of said housing recess in positions extending into said housing recess, said housing recess having sides receding in opposite directions away from said projections, respectively, on the side thereof opposite the side thereof on which said member is located; and a spring in said recesses having first and second opposite ends thereof adapted to fit into said first and second apexes, respectively, said spring being movable from a position in engagement with either one of said projections to a position in engagement with the other by movement of said member toward said housing, said housing having first and second spaced and parallel main flat surfaces partially defining said housing recess, said housing recess having surface portions defining the remainder of said housing recess, said surface portions being normal to said first and second main flat surfaces, said surface portions lying in mathematical surfaces described by moving a first line segment in a direction normal thereto while located between said first and second main flat surfaces normal thereto and having first and second ends located in the respective first and second main flat surfaces, said housing recess and said member recess being symmetrical about a plane normal to said first and second main flat surfaces midway between said projections and passing through said apexes, two of said surface portions being first and second auxiliary flat surfaces which intersect substantially in a second line segment normaL to said first and second main flat surfaces, which second line segment is effectively said second apex, said member having third and fourth main flat surfaces approximately in the planes of said respective first and second main flat surfaces, and partially defining said member recess, said member having third and fourth auxiliary flat surfaces normal to and extending between said third and fourth main flat surfaces, said third and fourth auxiliary flat surfaces intersecting substantially in a third line segment normal to said third and fourth main flat surfaces, which third line segment is effectively said first apex, said member and housing having flat facing sides with respective facing openings into the respective recesses therein, said spring being a straight metal leaf spring having a rectangular cross section uniform along its length, said spring being flat when unstressed, said motion direction means including a straight slot in said housing and having an opening through said facing end of said housing, said slot being symmetrical about a plane through said apexes and having a rectangular cross section uniform throughout a portion of its length thereinto from said opening thereinto, a straight rigid slide having a rectangular cross section uniform throughout its length fixed relative to said member and slidable in said slot, stop means fixed relative to said housing and engageable by said slide to limit movement of said slide in a direction out of said slot, said spring being column loaded between said housing and member apexes when said slide engages said stop means in a manner such that said spring takes a deflection so that it successively and substantially forms each one of both oppositely disposed arcs, said spring being movable to a first position engageable with one of said projections, movement of said spring from engagement with said one projection to a second position for engagement with the other being caused by a movement of said member toward housing, subsequent movement of said member to a position where said slide lies in engagement with said stop means making it possible to move said spring from said second position thereof to said first position thereof by again moving said member toward said housing, the transfer of said spring from said first position thereof to said second position therof, and vice versa, being successively possible substantially ad infinitum, said spring being bistable, that is, stable in each of said first and second positions thereof, said member and housing recesses being of widths only slightly greater than said spring to guide movement of said spring, said projections being located about two-thirds the maximum distance between apexes from the apex in said housing recess, said apex in said housing recess having a groove therein in which the end of said spring is held in cantilever fashion, each projection having a conductive switch contact engageable by said spring when it is in its respective first and second positions.