On Mon, 24 Sep 2007 17:21:26 -0500, Ignoramus3778
wrote:

Interesting discussion.

So, a good start would be a safety conversion from pedal to two switch
operation, right?

Oh, absolutely. And you want to put guards around anything that
moves just so someone doesn't get 'brain fade' and put their hand in
where it shouldn't go - only takes a fraction of a second of
inattention to make a batch of hamburger out of a hand.

The term you want is a "Two hand no tie-down" safety circuit, where
you have to push two buttons roughly at the same time. And the press
won't reset if one or both buttons is held down, as would happen if
someone deliberately jammed one of the buttons to get out of pressing
it each time.

Clippard makes one that's 100% pneumatic (logic control valves, like
air relays) if the machine is all air powered and air operated, and
you don't want to run electricity to it just for the controls.

-- Bruce --