holding mechanism

pps: final design V3 with a seating on one and a screw on the other side. Only 3 parts and can handle some torque.

ps: changed the design to a seating on one and an accentric (spiral) mechanism on the other side. Much lower hight, more stability, less parts (4 instead of 5). The first thought isn't always the best.

I needed a contraption that could hold down an object sturdily in one plane but also let it be released easily if you take it out of the plane. A mechanism that fits the bill is this bistable spring-operated flip-flop snapping mechanism I don't really know the name of. I thought I share some details I found out about it.
The main dimensions in the design process are a and b. a is the distance between the rotational axes, b is the perpendicular distance to the spring joint. For a given pair of a and b you get distance c, the distance the spring has to give from one stable end point to the other. I tried to come up with a single part compliant spring without a joint an