GB2158200A - High-speed protective check valve - Google Patents

Abstract

Sudden increases in fluid pressure which could be injurious to the diaphragm and seals of a sensitive capacitive pressure transducers, nanometers, or the like, are blocked automatically by a valve having an elastomeric closure (7) which is immediately propelled into a closed position as an abrupt pressure surge commences. The closure comprises a truncated conical or part spherical middle portion 7A making line-contact with the seat 8, and tapered and cylindrical end guide portions 7D,7B trapped within and guided by surrounding inner surfaces of the valve body. Threadedly-united halves of the valve body may be adjustably telescoped to adjust the limits of travel of the closure. <IMAGE>

Description

SPECIFICATION High-speed protective check valve The present invention relates to a high-speed protective check valve. More particularly, and in one particular aspect, the invention relates to a check valve of uncomplicated low-cost miniaturised construction which responds instantly and automatically to abrupt high surges of fluid pressure by blocking and sealing against the transmission of such pressures to vulnerable structure such as the diaphragm and seals of a capacitance manometer, and which is readily adjustable in response, having self-cleaning characteristics, and operates without externally applied power.

Fluid valves have of course been long known in many and varied forms, including that of the so-called "check" valve type in which fluid flow is essentially limited to one direction, as by a reciprocatable or hinged valve member, and sometimes involving spring-biasing or electromagnetic actuation.

However, when the application demands, in combination, extremely rapid response, very tight and sustainable valving closure, adjustable response, instant and positive closures with but minute gaseous flow, and wholly automatic high-speed operation not dependent upon power from an auxiliary source, it becomes necessary to improve upon what has been commonly available. For example, these demands present themselves in respect of valving which might protect delicate pressuresensitive devices against sudden large pressure bursts, as in the case of sensitive capacitance manometers whose thin diaphragms and relatively frail seals can be damaged when there is an almost explosive inrush or air upon a breaking open of a very low sensed pressure to a relatively high ambient atmospheric pressure.If injury during such episodes is to be avoided, the measurement inlet port to the manometer must be blocked tightly near the very onset of the pressure transient well in advance of the very brief time it takes the potentially troublesome ambient air pressure to assault the manometer from outside. That allows virtually no leeway for detection of abrupt pressure changes and for speedy actuation of valving members in opposition to their inertia. Moreover, the blockage or sealing must be of exceptional quality and integrity, otherwise leakage will negate the intended protective effects.Nor is it enought that the blockage be effected and sustained upon sudden increase of the pressure: it must also be possible for the valve to open widely very quickly and thereby allow the associated manometer to perform its intended pressure measurements during processing operations in which there are fluctations or alternations between high- and low- pressure conditions.

Preferably, the response of the valve should be adjustable, to meet the needs of different processing operations.

In accordance with the present invention, we propose a check valve capable of operating at sufficiently high speed, and with the needed quality of sealing, to protect a capacitance manometer or the like against damage from bursts of gas pressure, and having a lightweight free movable valving member or plug shaped to be fluid-propelled instantly from a gravity-induced "open" rested condition into a line-contact active "closed" sealing relation to a body seat as suddenly-increased fluid pressure seeks to propogate itself through the valve body and into the vulnerable manometer.A preferred embodiment of the invention comprises a valve body having two aligned ported parts threadedly engaged in an adjustable telescopically-enveloping relation to a one-piece freely-movable valving or plug member which is moulded of elastomeric material, the plug member having a truncated conical valving portion disposed for seating and line-contacting engagement with a stationary seat formed as a circular narrow edge about a passageway through one of the body parts.That conical valving portion merges with a slightly-tapered upper guiding end which is always mated loosely within the passageway and prevents the freely-movable plug member from becoming so cocked as to be likely to seat itself imperfectly; at its opposite lower end, the plug member exposes a relatively broad-area surface to impingement by onrushing gas, such that it will be propelled upwardly aginst gravitational forces and its conical portion will seat and seal with the stationary seat.When the external pressure matches or falls below that within the manometer, gravity quickly induces the plug member to drop from its seated "closed" orientation, thereby opening the manometer for measurements of low pressures; that fall in pressure may occur in the normal course of operation of the manometer, or the inside and external pressures may equalisize gradually and without risk of damage to the manometer as the result of relatively slow leakage which is permitted through the check valve. Response of the valve can be adjusted by tightening the threadely-connected body parts and thus restricting allowable travel of the plug member housed within them.

The present invention enables a high-speed protective check valve to be of uncomplicated, reliable, inexpensive and adjustable precision construction and to be capable of instantly blocking the passage of potentially troublesome effects of fluid pressure surges and immediately restoring operative open-valve conditions when required.

According to one feature of the present invention, we propose a protective high-speed check-valve, for capacitance manometers and the like, wherein a lightweight movable resili ent plug member is shaped and disposed to be swiftly fluid-propelled into a seated sealing which effectively blocks transmission of harardous bursts of fluid pressure, a normally-open condition being maintained or restored by gravity.

Other features of the present invention are set forth in the appended claims.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a high-speed protective check valve in association with a schematic representation of a capacitance manometer, the movable valving member and its seat being indicated by broken lines; Figure 2 is an explded cross-section of a high-speed protective check-valve; Figure 3 is a longitudinal cross-section of the assembled check valve (the movable plug member being only partly sectioned); and Figure 4 shows a detail, partly in crosssection, of an interior portion of the valve.

In the drawings, like reference characters designate identical or corresponding components and units throughout several views. Fig.

1 shows a high-speed protective check valve, 5, which includes axially-aligned inlet and outlet couplings, 5A and 5B, respectively, at opposite ends of a main valve body member 5C. That valve is disposed in the gaseous-fluid line between a capacitance manometer 6 and some site at which gas pressure is to be monitored, such as an evacuated site being maintained at very low pressure in connection with the processing of electronic semiconductor items.The example of a capacitance manometer 6 which was chosen for discussion purposes is a sensor of a single-sided absolute-pressure type in which capacitor electrodes 6A and 6B are disposed within an evacuated and sealed "reference" pressure side 6C of the envelope 6D and are connected externally into measurement equipment (not shown) which responds to such of their capacitive relationships as are influenced by pressure-induced deformations of a relatively thin metallic diaphragm 6E. Depending upon what pressures are communicated to the "sensed" pressure side 6F of the unit, the diaphragm 6 E may deflect to a greater or lesser extent, as indicated by the broken line 6E', and related capacitance measurements will characterise those pressures.Certain of the structural niceties by which such manometers are designed to have needed sensitivities are also potential sources of difficulty, as in the case of the thin diaphragm 6E, in particular, that diaphragm must be resilient deformable enough to response repeatedly in a predictable way to both slight and major pressure changes and yet must not be allowed to exceed its elastic limits nor to impact with nearby structure nor to overstress its supports and seals. There is an exceptionally high degree of vulnerability when the sensed pressure bursts abruptly to a high value, typically and quite frequently when the system undergoing measurement is suddenly vented to atmospheric pressure.On such occassions, the diaphragm can be violently shocked and distended, with strong likelihood of injury and malfunctioning, especially after such operational punishment has been inflicted repeatedly.

The rapidity with which the large pressure bursts occur suggests that any useful protection should be approached through electronically-controlled high-speed electromagnetic valving, a solution which would entail costly and complicated equipment, as well as reliance on a power supply. However, it is found that the naturally-powered check valve 5, which operates entirely without an auxiliary supply of energy and depends instead upon gravity and forces developed by gases within it, can reliably afford adequate protective checking at appropriate speed and with tight closures.For those demanding purposes, the needed valving is implemented by a small and lightweight movable plug member 7 which is moulded of elastomeric material and has a truncated conical mid-section designed to seat intimately in line-contact relationship against a narrow circular edge 8 between stepped inner surfaces of the valve body 5C. That midsection, 7A, and the narrow band 9 along which it engages the seat edge 8 about a third of the way down from its narrower end, are shown in enlargement in Fig. 4, with the essentially line-contact band 9 being designated by a row of small crosses. The slope angle of that truncated conical section is preferably about 45 degrees to the longitudinal axis 10-10 of the plug member and valve assembly, that relatively steep slope being adequate to guard against the plug becoming inadvertantly wedged into and stuck in its seat.

The illustrated check-valve is intended to be mounted with its longitudinal axis 10-10 essentially vertial, so that the small plug member 7, exceedingly lightweight as it is, will normally gravitate to rest in a lowered position (not illustrated) against an annular inner shoulder 11 (Figs. 2 and 4) of the inner valve body part 5D integrally associated with the inlet coupling 5A. A lower cylindrical portion 7B, of the plug member is disposed to rest against that shoulder and to present its planar circular bottom surface, 7C, in a perpendicular relation to the direction of any onrushing burst or air or other gas, the latter being characterised by arrows 1 2 (Figs. 3 and 4). When the system site at which pressure is being measured is being evacuated or otherwise reduced in pressure, related gas flow through the check valve is in the direction of arrow 1 3 (Fig. 1), clearing the resting plug member 7 by flowing downwardly around its first through annular clearance spaced between cylindrical portion 7B and a surrounding sleeve 14 at the upper end of the body 5D and then through an array of hemi-cylindrical recesses 15 bored downwardly from the annular shoulder 11.However, when there is a sufficiently abrupt and intense reversal of gas flow, into the manometer in the direction of arrow 1 6 (Fig. 1), as will occur when an evacuated measurement site is suddenly vented to atmospheric pressure, the burst or air impacts forcefully against blunt end 7C of the plug member as characterised by arrows 1 2 (Figs. 3 and 4), creating a strong lifting force which at once propels the lightweight plug member upwardly at high speed into a firmly-seated tightly sealed relationship with seat edge 8. That action takes place with such rapidity and sureness that the manometer is not required to withstand the main brunt of the pressure burst, the protective blocking or checking occurring well before the manometer can be unduly shocked with pressure.

Moulded plug member 7 is formed in a single-piece comprising not only the aforementioned truncated conical mid-section valving portion 7A and a lower cylindrical base portion 7B but also an upper guide portion 7D. Preferably, that guide portion tapers slightly narrower in the upward direction, and it is long enough to remain well mated within the bore 5E of body portion 5C even when the plug member is at its lowermost possible position. The mated and guiding relationship insures that the plug member cannot become so tilted or cocked that it might catch and not immediately seat properly when thrust forcefully upwardly by an onrushing burst of gas.

The small plug member 7 may typically be only about 0.48 inch in maximum lowermost diameter and 0.36 inch in minimum uppermost diameter, when moulded of a 70-durometer hardness fluoroelastomer such as that commercially available under the commercial designation "Viton-A" (R.T.M.), is merely about three thousandths of a pound. Other materials or combinations of materials may be used effectively, although it is preferred that the valving surface be of a resiliently-deformable material such as a common rubber or elastomeric plastic, allowing for tight seating under but slight pressure. In addition, the flexing elastic character of the valving surface tends to self-clean or oppose build-up of contaminates which could impair sealing.The aforementioned taper angle of about 45 degrees is highly satisfactory in respect of a good non-wedging line-contact seal being made between the truncated conical mid-portion 7A of the plug member and the narrow edge seat 8 in the upper body portion 5C. At much shallower angles, the plug member cannot be expected to centre itself as well in its seat, and the sealing may vary as to position and be less even. Seat edge 8 is so proportioned in diameter that it tends to engage and seal with the truncated conical valving portion 7A of the plug at about one-third of the way from its narrower end to its larger-diameter end, as represented by numeral 9 in Fig. 4, it being found that centering and little sticking occurs under those conditions.Were the taper angle significantly steeper, the plug member could tend to deform and wedge itself within the seat, making release and opening of the valve uncertain. In the latter connection, it should be noted that although the valve closes as a result of the force of onrushing gas against the larger end 7C of the plug member, it drops and opens when the downward force of the mass it exhibits under influence of gravity is greater than the amount by which the upward force of gas pressure from below exceeds the downward force of internal manometer gas pressure from above. Effective areas of the plug member exposed to those gas pressures are essentially the same, such that differentials in pressure, not area, affect the valve openings. Too light a plug member tends to open sluggishly however.

Sensitivity of valve operation is affected controllably by adjustment of the axial distance through which the valve plug member 7 must move between its lowermost (open) and uppermost (closed) position. For those purposes, the upper lower valve body members 5C and 5D are mated by way of their cooperating internal and external threadings 5C' and 5D', respectively, and they can thereby be more drawn together or separated, axially, by appropriate manipulation of their knurled exterior surfaces 5C" and 5D", respectively.

The cylindrical lower portion 7B of plug 7 fits somewhat loosely within a cooperating cylindrical recess 14' (Fig. 2) in the sleeve 14 at the upper end of body member 5D and, when the valve is in an "open" condition with the plug at its lowermost position, the edges of the planar bottom 7C of the plug rest upon the aforementioned cut-out annular shoulder 11. Therefore, depending upon how fully the two body members are mated together, the plug member will have a selectably shorter or longer distance to travel axially upward along axis 10-10 before it engages seat edge 8 and effects "closing" of the valve and "checking" of a pressure burst.The sensitivity adjustment is in the nature of a micrometer manipulation, in that, before the valve is installed, the operator rotates the body members in direction to draw them together about the plug member inside until shaking along axis 10-10 no longer yields the rattling sound which is otherwise caused by the plug member's freedom to move, and then an opposite direction rotation of one body member relative to the other by a predetermined angular amount draws them apart by a predetermined axial amount which frees the plug member from an entrapped "zero" and unmovable position so that it may move axially by that predetermined axial amount. Fineness of the threading determines how much angular movement will produce predetermined axial separation of the body member, and, in turn, the sensitivity of the valve to pressure changes.In one embodiment, each one-third back-off turn from "zero" was effective to increase the checking pressure requirement by about one torr, for example.

Leakproof coupling of the relatively-rotatable body members is assured by an O-ring seal 1 6 fitted in a groove 1 7 at the upper end of body member 5D, the upper body member 5C having an internal bore 18 with a cylindrical surface by which the O-ring is compressed to block leakage. Coupling of the threaded upper end of body member 5C with a manometer inlet or the like is facilitated by an internally-threaded nut 1 9 which forces a hollow sleeve 20 against a sealing O-ring 21 rested upon a sloping shoulder 21 spreading radially from near the uper end of member 5C; when the O-ring 21 is sufficiently compressed, it is distended radially inward and thus seals against a manometer inlet tube (not shown) mated closely within it.

The valve installation is preferably essentially vertical, although operation off vertical up to about 45 degrees is possible, with some degradation in performance. Where gravity alone is not to be relied upon for the automatic opening, a spring, magnetic or other biasing may be introduced to normally urge the plug member away from the seat. A onepiece moulded plug member, such as has been described and shown, is preferred, and its truncated conical valving portion can readily be moulded very precisely and entirely without mould lines which would otherwise tend to interfere with optimum seating and sealing. In other constructions, the truncated conical portion of the valving member may instead by spherically, rather than conically, contoured, although a full ball member would of course exhibit undesirable mould lines and would therefore not be a good substitute. The illustrated planar bottom surface of the plug member may alternatively be concave, and the entire member may be hollowed out from that end to achieve lightness with broad area against which the onrushing gas can impinge to develop the checking action. A single-piece moulded plug is preferred, with no seam lines except that at the intended corners and edges, but useful results could be attained with a comparable multi-piece plug member and/or with a non-resilient core piece carrying a sheath of elastomeric sealing material along the truncated valving section of the plug.

Claims (10)

1. A high-speed protective check valve for pressure transducers and the like comprising a valve body having inlet and outlet ports communicating with an interior fluid flow passageway which extends along an axis therethrough and has a narrow circular edge defining a valve seat normal to the axis, a valving member contained within the body and guided about its exterior for short reciprocating movements along the axis between a first flowblocking position in which an exterior valving portion thereof engages and seals with the seat and a second position at which the member is axially displaced from the seat and fluid may flow around the member and through the seat and the passageway, the exterior valving portion of the valving member being resiliently deformable and having an exterior configuration which is a surface of revolution about the axis diminishing in diameter from a larger end of the member to a smaller end portion which is of lesser diameter than the seat and fits therethrough to allow the seat to make essentially line-contact seating and sealing with the exterior portion, the larger end of the valving member being closed by surfaces disposed substantially normal to the axis and being fitted within the passageway to have relatively large amounts of onrushing fluid headed past it toward the seat impinge directly upon the larger end and thereby to propel the valving member along the axis until the exterior portion seats and seals itself in an essentially line-contact engagement with the seat, and the smaller end portion of the valving member being of sufficient axial length and diameter to extend through the seat irrespective of the axial position of the valving member and to prevent the valving member from tilting excessively about the axis and becoming jammed, the valving member being of such light weight in relation to forces developed by impingements of onrushing fluid upon the larger end thereof as to allow the valving member to be propelled into a seated and closed condition rapidly when the onrush commences and, thereby, to protect against passage of significant bursts of fluid therethrough.

2. A check valve according to claim 1 wherein the exterior valving portion of the valving member is of elastomeric material and of truncated conical configuration, and wherein the valve seat is formed by stepped inner surfaces of the valve body which merge at substantially 90 degrees at the site of the narrow circular edge.

3. A check valve according to claim 2 wherein the valve body comprises two body members mated by way of complementary external and internal threading coaxial with the axis and the passageway, one of the body members having one part of the passageway and the valve seat therein, and the other of the body members having another part of the passageway and a recess accommodating the larger end of the valving member therein, the threaded body members being relatively rotatable about the axis to adjust the axial separations between the first and second positions and, thereby, the sensitivity of the check valve to pressures which will close the valve.

4. A check valve according to claim 3 wherein the valving member is mechanically unconnected in relation to the body and comprises a free single-piece member moulded of elastomeric material without mould lines along the valving portion of truncated conical configuration.

5. A check valve according to claim 4 wherein the valving portion of truncated conical configuration tapers from the larger end to the smaller end portion with a slope of about 45 degrees in relation to the axis, and wherein the narrow circular edge defining the valve seat is of a diameter which causes it to engagfe the valving portion at about one third of the axial distance from the smaller end portion to the larger end when the valving member is seated therewith.

6. A check valve according to claim 5 wherein the smaller end portion of the valving member tapers down to a relatively small angle from the valving portion to the free end thereof, and wherein the larger end of the valving member is substantially cylindrical and has a blunt end surface substantially normal to the axis in position to be impinged by the onrushing fluid.

7. A check valve according to claim 6 wherein the substantially cylindrical larger end of the valving member is accommodated relatively loosely within the recess in the other of the body members, the recess being at the inner end of the other of the body members and having an annular shoulder at the bottom thereof and around the fluid passageway therethrough, the shoulder being disposed for interference with edges of the blunt end surface of the valving surface to establish the second position of maximum axial displacement of the valving member from the seat, and the shoulder having relief passagewats therethrough to permit by-pass flow of fluid around the valving member when the blunt end surfaces of the valving member rest on the shoulder.

8. A check valve according to claim 7 wherein the axis is substantially vertical and the said one of the body members is situated atop the other of the body members, whereby gravity urges the valving member toward the second position to open the valve.

9. A check valve according to claim 4 wherein the valving member is of a fluoroelastomer material and has about a 70 durometer hardness, wherein the axis is substantially vertical, wherein the second position is below the first position, aND wherein the valving member is urged toward the second position by gravity to open the valve in the absence of countervailing lifting forces by the onrushing fluid and by greater pressures below the valving member than above it.

10. A high-speed protective check valve constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.