Double diaphragm precision throttling valve

Abstract

A throttling valve assembly actuated by a stepper motor having a double diaphragm seal and integral throttling surface. The throttling surface interfaces to a mating orifice and port arrangement to provide a smooth control regime for various process fluids. Because of the unique design of the flow paths, the fluids will remain in a laminar flow state throughout the throttling range, thus providing smooth and continuous response to the control input. The valve opening to the fluid is controlled by a stepper motor through a direct drive mechanism. The embodiment shown here employeesemploys all PTFE construction for the wetting parts, but any material could be used that would be compatible with the process fluid. Additional features are minimal capture of the process fluid, free draining, and no metallic parts in close communication with the process fluid.

Description

FIELD OF INVENTION[0001]The present invention relates to fluid control devices and in particular to those applications where materials of construction must be compatible with the process fluids and where it is a requirement that minimal volumes of fluids are captured within the valve. Often times the only suitable material meeting these requirements will be PTFE or other Teflon types. Furthermore, these applications often require that no cracks or crevices are present to permanently capture fluids or particulate carried by the fluid. Another requirement where slurries are being controlled is that the fluid should not be subjected to high rates of shear. Lastly, these fluids are often highly toxic and a double containment is necessary for any thin walled barrier in contact with the fluid.BACKGROUND OF INVENTION[0002]Many forms of throttling valve are found within the field. Viraraghavan describes a valve in patent '530(cited in the references) that that is typical of valves that may,...

AI Technical Summary

Benefits of technology

"The invention is a valve that allows for a smooth flow of fluid with minimal internal volume and no cracks or crevasses. It includes a thin walled diaphragm that can seat down on a valve to close off the flow path and retract to offer decreasing resistance to fluid flow. The valve body is made from a solid block of homogeneous material, such as Teflon, and contains an inlet, a cavity, a moveable diaphragm, and a throttling surface. The diaphragm is flexible but strong enough to withstand fluid pressures up to 60 psi. The valve assembly is housed in an outer housing for protection. The technical effects of this invention include improved flow control, reduced noise and wear, and the ability to detect leaks."

Problems solved by technology

This introduces both small cracks and crevasses, as well as another material(the o-ring) that may not be compatible with the process fluid.

Here a metallic actuation shaft is buried in the flexible diaphragm such that it is susceptible to corrosion from ionic migration from some process fluids.

Secondly, this valve contains a large number of parts of metallic content as well as a comparative large volume of fluid should the primary diaphragm fail.

Generally valve designs described in the art attack one or two of the problems described, but none approach the whole problem of safely handling highly toxic or corrosive fluids while providing a smooth continues laminar flow in a free draining, low captive volume device.

Many fluids are both hazardous and suffer detrimental effects to sheer effects when flowing around such obstructions.

Any configuration that results in the flow response being linear over a portion of the range and transitioning to square law at some point will have a detrimental effect on the ability of the controller to smoothly regulate the flow.

Generally drive mechanisms described in the references were judged as incapable of continuous repositioning, or would exhibit excessive backlash detrimental to smooth fluid control.

Images