more an OpenScad exercise than a thing, but still may prove usefull :
this is a fully parametric model that can be use to explore and visualize different configurations of a rotation to translation mechanism using the "punching machine" principle.

Download, start animation mode, and try new axes and arms configuration.

The default one features a nice autolock mode at maximum extension (135°)

Too bad, i uploaded an animated gif but it shows as a still... you can download it from the source files section

first, you should download the source file and start the animate mode in openscad.
now you can try and text parameters :
Bx,By to position the fixed pivot point of the pucher
Ax,By to position the fixed pivot point of rotation source
ra1 and ra2 for the length of the punching arms
r1 and r2 for the radii of the rotating arms
not all values will lead working results.
coming soon :
a "print mode" , in order to layout the parts in a printable way