Pneumatic circuit to provide different opening and closing speeds for a pneumatic operator.

摘要

A pneumatic circuit prolongs a pneumatic valve (20) opening time using an accumulator with two quick exhaust type valves (36, 46) in series while providing a rapid valve closing time. This structure and method is self-contained and amenable to retrofit in existing installations without any external connections. Slow opening is achieved by routing inlet gas pressure simultaneously to an accumulator (51) and the operating cylinder (21) of the valve to be opened. A tortuous piping path (61, 36, 62, 63, 44, 46) and increased volume to be pressurized due to the addition of the accumulator (51) substantially reduces the isolation valve opening time, thereby eliminating problems associated with quick opening of a pneumatic valve. When the pneumatic valve (20) needs to be closed quickly, slight venting toward the inlet valve (29) immediately causes the quick exhaust valves (36, 46) to vent (39, 49) their downstream pressure. The accumulator (51) then vents through its quick exhaust valve (46) while separately the main quick exhaust valve (36) quickly vents the air cylinder (21) of the pneumatic valve. Closing times penalties of less than 50 milliseconds can be achieved using this configuration and opening times can be increased by adjusting the volume of the accumulator.