Patent ID: 6708771
Filing Date: 2004-03-23
Classification: A62C

Abstract:
An electro-pneumatic actuator for depressurizing a piston reciprocable within a cylinder charged with a pressurized first fluid, said actuator adapted to be in fluid communication with a source of pressurized second fluid and comprising:a first chamber having a flexible first diaphragm mounted therein and sealingly dividing said first chamber into first and second chamber portions, both said chamber portions being in fluid communication with said cylinder, said second chamber portion having an opening providing fluid communication with the ambient, said opening being surrounded by a seat facing said first diaphragm, said first diaphragm being deflectable into sealing engagement with said seat to seal said opening when said cylinder is charged with said first fluid; a second chamber having a flexible second diaphragm mounted therein and sealingly dividing said second chamber into third and fourth chamber portions, said third chamber portion being in fluid communication with said source of pressurized second fluid, said fourth chamber portion being in fluid communication with the ambient and having an aperture providing fluid communication with said first chamber portion, said aperture being surrounded by a second seat facing said second diaphragm, said second diaphragm being deflectable into sealing engagement with said second seat to seal said aperture when said third chamber portion is pressurized with said second fluid; a third chamber having a flexible third diaphragm mounted therein and sealingly dividing said third chamber into fifth and sixth chamber portions, said fifth chamber portion being in fluid communication with said pressurized first fluid, an elongated plunger having one end positioned within said sixth chamber portion and engageable with said third diaphragm, the other end of said plunger being positioned within said third chamber portion and engageable with said second diaphragm, said third diaphragm being deflectable into engagement with said one end of said plunger when said fifth chamber portion is pressurized with said pressurized first fluid, said plunger being thereupon forced into engagement with said second diaphragm and thereby forcing said second diaphragm into sealing engagement with said second seat; a passageway providing fluid communication between said fifth chamber portion and the ambient; a valve engaged with said passageway and having a valve member movable between an open position allowing fluid flow through said passageway, and a closed position preventing fluid flow through said passageway, said valve further having means for biasing said valve member into one of said closed and open positions and an electrically operated actuator for moving said valve member against said biasing means and into one of said open and closed positions; and said second diaphragm being deflected out of engagement with said second seat only when fluid pressures in both said fifth and said third chamber portions are lowered to respective predetermined values, pressure in said fifth chamber portion being lowered by electrically actuating said valve member into said open position, pressure in said third chamber portion being lowered by a drop in pressure of said pressurized second fluid, upon deflection of said second diaphragm, pressurized first fluid in said first chamber portion being permitted to enter said fourth chamber portion and exit to the ambient, thereby allowing said first diaphragm to deflect out of engagement with said first seat and allowing pressurized first fluid to flow from said cylinder through said second chamber portion and exit to the ambient, thereby depressurizing said piston and allowing it to move within said cylinder.