Multi-screw press

I was looking at the press in
https://www.youtube.com/watch?v=K25dnGpwZyU

which is a screw press with four screws at the corners of a square block.
Thought, I have got all the bits I need to build one of those, except the bits to turn the screws. Then thought, how do I turn the screws?
I guess they must turn together, but would they be locked together to keep the plates parallel?
Eg, a single gear turns four gears at the ends of the shafts. Problem then is, the force on the single gear is kinda large, and the four gears have to be quite large and thus expensive too, and for geometric reasons you can't use a small central gear to get a large turns ratio (the four gears would interfere with each other).
Any other thoughts on how to turn the screws?
-- Peter Fairbrother
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"Peter Fairbrother" wrote in message

Peter,
The four screws are used for coarse adjustment of the 'daylight' of the press (not the main squashing), and the force is being produced hydraulically by an upstroking cylinder.
My 60 ton press has a similar arrangement of four screws that in mine suspend the platen, and the cylinder is downstroking. The screws on mine are joined by a continuous chain running on sprockets driven by a 1 hp motor. Mine has thrust bearings on the screws to reduce friction, that sit on massive springs that are so arranged that as the hydraulic force comes on, the springs compress and a collar seats on the platen preventing the bearings taking the force. That feature confused me when I got it. The press had been in a catastrophic fire that melted it's hydraulic pump and chain drive motor, and also it turned out de-tempered the springs. It took a while to work out how it should work, then a bit of calculation to find the correct spring rate to have new springs wound out of 6 mm spring steel !
Andrew
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On 27/03/15 12:35, Andrew Mawson wrote:

Thank you Andrew (a very nice chap), that was most informative.
It also answered my unspoken concern about using standard threads rather than acme threads - if they are not in tension when they move, then the extra friction won't matter.
Hmmm, back top the drawing board. Operating area of the press will be about 4" square only, it's for small parts - so maybe a 32-ton bottle
http://www.ebay.co.uk/itm/32-Ton-Heavy-Duty-Hydraulic-Bottle-Jack-Lifting-Ram-Car-Van-Boat-Truck-Lorry-30-/400647364630?pt=LH_DefaultDomain_3&hash=item5d4871a016
I don't think I'll bother with the thrust bearings.
Thanks once again.
-- Peter F
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