Variable vain (or pitch) computer fans?

Has anyone released any of these fans for computers before?

Variable vain just means you can change the angle of the blades to increase the amount of air a fan can push. the blade design would have to be differant, but it would be worth on somthing that can wind up as far as a delta. Changing the pitch of the blades and slowing the fan would reduce fan noise a lot too.

I like the idea, but it is along the lines of those fans that had the motor magnets in the corners and the coils around the outside of the fins so that the middle is free of dead spots - brilliant idea but died off like most brilliant ideas.

I would make use of the centrifugal effect. Make it so that the faster the fan turns the steeper the angle becomes to scoop more air.(put weights on the fins or something) At slow speeds the low angle of attack should make less noise.

bumpity bump bump

anyone else have any thoughts?