It sounds like you have an Interact 4. This had a hydraulic cylinder up top to push on the drawbar. Because this may need in excess of 1500 pounds of force they use a air amplifier to push on a master cylinder at the base of the machine. Very similar to how a hydraulic jack works. It gives you a calculated mechanical advantage. The air cylinder has a certain diameter working with so much air pressure. It works against a hydraulic cylinder. The ratio is 25 to 1. Thus if you put 100 PSI into the cylinder, it produces a force of 2500 psi at the hydraulic cylinder. I have used a similar contraption to fill 3000 PSI scuba tanks from a 2000 PSI source (and 4000 PSI paintball tanks from a 120 PSI source). It all depends upon the ratio of the amplifier.
I have had problems on the earliest Interact with leaks and being trapped in the cylinder. This consumes a certain amount of the capacity of the system to compress the trapped air and may not have enough stroke to release the tool.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)