Precision flow controller

An improved flow-controlling mechanism utilizes interference-fitting components and static seals to assure accurate and repeatable fluid flow-controlling settings and to eliminate a leakage deteriorating seals.

BACKGROUND & SUMMARY OF THE INVENTION 
Fluid-flow controlling valves commonly rely on the force exerted by a 
resilient member against a valve seat to control the flow of fluid through 
the resulting aperture. The flow-controlling force is usually established 
by a jack-screw arrangement of a rotating shaft within the valve body. One 
disadvantage of a flow controller of this type is that the rotating shaft 
has to be sealed against leakage where the rotating shaft protrudes 
through the valve body. Where such a valve controls pervasive or corrosive 
fluids, such a dynamic seal can deteriorate and destroy the integrity of 
the fluid system. 
In accordance with the present invention, a pair of mating valve members 
are arranged to cooperate via interference fit to control fluid flow 
therethrough with high precision and repeatability of setting. In 
addition, an integral member provides static seal of fluid within the flow 
controller as the two valve members undergo relative movement. This 
assures more reliable bilateral flow control than is possible with 
conventional valves.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, there is shown a sectional view of one embodiment 
of the present invention. The present flow controller includes the body 9 
and stem 11 and integral diaphragm 13 which are generally cylindrical in 
shape (not shown) and which are formed of a resilient, deformable material 
such as tetrafluroethylene resin known as TEFLON supplied by DuPont 
Company. The inner stem 15 of cylindrical shape engages the cylindrical 
aperture 19 in the body 9 in interference-fitting fashion, i.e. the 
diameter of the inner stem 15 is larger than the diameter of the aperture 
19. However, since the body 9 is also formed of a resilient, deformable 
material such as tetrafluroethylene resin (e.g. TEFLON), the two members 
conveniently slide one within the other to establish a positive fluid 
seal. The flow controlling properties of these two members is established 
by a tapered groove 17 formed longitudinally within the wall of the inner 
stem 15, as illustrated. Thus, fluid under pressure can pass only through 
the groove 17 from one side of the seal to the other, and the volume of 
fluid under pressure per unit time that passes through the flow controller 
is determined by the length of the tapered groove 17 which protrudes out 
of aperture 19. Fluid may thus flow in either direction between parts 21 
and 23 with comparable precision and flow characteristics. 
The length of groove 17 which protrudes from aperture 19 is determined by 
the rotation of the threaded knob insert 25 relative to the members 9 and 
11. The mating threads 27 are carried on plunger 29 which is rigidly 
attached to the member 11. Thus, rotation of the knob and insert 25 
relative to the plunger 29 converts this rotational motion into 
translational motion of the stem 15 and groove 17 into and out of the 
aperture 19. Suitable thrust bearing arrangements on the knob and insert 
25 including flange 31 and retaining ring 33 assure that the translational 
movement of the plunger 29 is proportional to the rotation of the knob and 
insert 25. 
The diaphragm 13 which is integrally formed on the valve member 11 is 
clamped around its outer periphery against the body 9 by the outer housing 
member 35 which is threaded 37 into engagement with the body 9. This 
provides a permanent, static seal of fluids within the body 9 and also 
holds the stem 15 and plunger 29 attached thereto against rotation with 
the knob and insert 25. This diaphragm is sufficiently thin and flexible 
to allow the plunger 29 and stem 11 and inner stem 15 to move 
translationally in and out of the aperture 19 without altering or 
affecting the fluid seal provided thereby. 
Referring now to the perspective view of FIG. 2, there is shown the 
generally cylindrical shape of the valve member including stem 11 and 
inner stem 15 and diaphragm 13, all formed as an integral structure of a 
material such as TEFLON. The plunger 29 is rigidly attached to the stem 11 
so that it cannot rotate with respect thereto. The tapered groove 17 
longitudinally oriented along the surface of the inner stem 19 provides 
the varying orifice for fluid flow therethrough as a function of 
translational movement of the member within the aperture 19. The diameter 
of the stem 11 may be selected to provide close-tolerance fit rather than 
inteference fit within the aperture 19 to serve as an alignment guide with 
the body.