| 摘要 |
A back pressure valve employing a spring loaded diaphragm normally closing a discharge port or orifice combined with a push rod extending externally of the valve for coupling with a control actuator with the inner end of the push rod being operatively associated with the diaphragm for using an external control system for varying or regulating the back pressure in a fluid flow line. In one embodiment of the invention, the push rod is engaged directly with the diaphragm assembly, whereas in a second embodiment of the invention, the push rod is engaged with the spring which in turn is engaged with the diaphragm assembly. In both embodiments of the invention, a weak spring is associated with the diaphragm to bias the diaphragm to a closed position to prevent passage of air to a pump intake in the event the system is shutdown with the control actuator and push rod in a position to leave the diaphragm open or to relieve pressure on the heavier main diaphragm spring.
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