Here are some pics of a Vacuum Chamber I have built.
It uses a Welsh labratory type, vanes in oil vacuum pump.
The lid is 1.5" lexan. Chamber itself is 1/4" plate SS.
Lid is on ball bearing slides. It moves like an ice cream chest.
Lid has air cylinders that lift it. Rolls back by hand.
When vac switch is truned on, vac pump starts, then when lid is 
  fully forward, lid is pulled down, and evacuation of air begins.
When switch is turned off, compressed air is admited to the 
  chamber to speed in opening. When pressure has equilized
  sufficently, the lid pops up, and the air shuts off. 
Lid may now be rolled back to open. Fully automatic.
Only one user switch. Full 1" vac hose to pump, no valving 
  restrictions. Works very well.
--Doozer in Buffalo