There are some principles that I may not understand about the vacuum door locking system. I hope you don't mind if I supply some drawings and ask some simplistic questions...
The images are a diagram of a theoretical vacuum door locking mechanism. At first I thought the diagram should have a sprung diaphragm in the middle, but I've realized that idea must be incorrect; the arm that extends from the vacuum mechanism must be mounted on a cylinder which moves up and down, or an unsprung diaphragm. I came to this conclusion because I realized that the mechanism do not return to some default state when vacuum is not applied; the arm remains in its current position when there is no vacuum present.
The first diagram shows a vacuum unit where vacuum has been applied to the unlock side of the unit. The diaphragm (or cylinder) moves toward the side where the vacuum is applied because the atmospheric pressure presses the opposite side. If we assume an atmospheric pressure of 14.7 psi and we apply a 20 psi vacuum to the unlock side of the unit, there there will be about 34.7 psi of pressure forcing the diaphragm to the unlock side on the unit.
The second diagram shows the same vacuum unit with 20 psi of vacuum applied to the lock side of the unit. Again, the diaphragm will move to the lock side because of the difference in air pressure on the -20 psi side and the +14.7 psi side of the diaphragm.
It is important to remember that for either condition, if the vacuum is lost, the unit does not attempt to change its state. If a locked vacuum unit loses all vacuum on the lock side, it stays locked; and conversely for the unlocked state.
So my first questions:
- Do the vacuum units fundamentally work in the described fashion?
- Is it true that what moves the diaphragm from one position to the other is the pressure differential on the two sides of the diaphragm?