METHOD AND APPARATUS FOR DELIVERING OIL TO A MULTI-STAGE PUMP

摘要

A method and apparatus for delivering oil into a pump chamber of a high-vacuum stage of a multi-stage pump. The method includes the steps of sensing a first pressure at an intake region of the high-vacuum stage of the pump, and sensing a second pressure at a discharge region of the high-vacuum stage of the pump. Oil is delivered to the high-vacuum stage of the pump in response to a pressure difference between the first and second pressures. Increased quantities of oil are delivered to the high-vacuum stage of the pump when the pressure difference exceeds a predetermined value. A gas ballast may also be delivered to the high-vacuum stage of the pump when the pressure difference exceeds this predetermined value. The apparatus may include a diaphragm valve including a diaphragm mounted between subchambers that are respectively in fluid communication with the intake and discharge regions of the high-vacuum stage of the pump. When the pressure differential between the intake and discharge regions, and thus the subchambers, reaches a predetermined level, the diaphragm is distended to a sufficient degree to unseat a valve element, which allows increased quantities of oil to be delivered to the high-vacuum stage of the pump.