| 摘要 |
A cyclic or periodic event timing system for use in conjunction with a pressure fluid control circuit includes a cylinder and piston type actuator comprising a differential area piston which is exposed to fluid pressure from a flow conduit on opposite sides of a flow restricting orifice in the conduit or a branch portion thereof. The actuator piston includes a rod portion which is extended in one direction in response to an unbalanced pressure force on the piston. On the extension stroke, the actuator opens a valve to effect flow in the conduit resulting in a reduction in pressure which is sensed in the cylinder chamber exposed to the larger piston fluid area. The actuator piston then returns to an initial retracted position in response to an unbalanced pressure force. Improved pneumatic process control systems utilizing the event timing actuator are disclosed including reverse air pulse type cleaning system for an air filter having a plurality of valve actuated jet nozzles operable in timed sequence by a version of the actuator with a rotary cam connected to the timer piston. A negative pressure filter system includes blow-in doors for reverse pulsing the filters with air at atmospheric pressure, each door being operated by actuators timed in their operations by the cylinder and piston timer actuator. A bulk material bin dump and air blast control system for dislodging stuck material is actuated by the timer actuator interposed in the system control circuit.
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