Hi Michel,
There really aren't many utilitarian convex blades that I can think of.
There are a few WWII US machete variants based on a Philippine bolo, with a wide belly and various convex curvatures. Not much thought into this, but it seems that a highly curved convex blade is not really needed for utilitarian purposes - cutting vegetation, wood, or rope
As far as i understand it, in lay usage "machete" covers pretty much any large blade that is not a recognizable sword or sabre. Technically I think of it as a relatively thin blade with no distal taper, mostly straight with parallel edges and with a sometimes broader convex tip, used primarily for cutting vegetation. Variations are endless. It would be good to see others chime in on this, as I'm not a native English speaker.
English is not always that precise. A while back there was a discussion around the difference between knife and dagger, bowie-type versus naval-type. Same as in French to some degree - couteau, poignard, dague, coutelas, subtle differences, all debatable.
Regards,
Emanuel