CA1100013A - Method of controlling bypass flow and article employing same - Google Patents

Abstract

APPLICATION OF: LAWRENCE A. KOLZE
FOR: METHOD OF CONTROLLING BYPASS
FLOW AND ARTICLE EMPLOYING
SAME

ABSTRACT

A flow control device having a bypass flow feature effective for achieving controlled flow at relatively low pressure differentials. A resilient flow control member having a recessed, downstream face is contained within a cylindrical fluid chamber defined by a housing having an inlet and outlet passageway.
A plurality of lobes formed around the periphery of the flow control member permit bypass flow through the circumferential spaces between lobes and the internal diameter of the fluid chamber. The flow control member has a centrally located orifice axially aligned with the inlet and outlet passageways of the housing. A plurality of projections are formed on the downstream face of the control member and are located near the outer periphery thereof while another set of projections, also located on the downstream face of the control member, are spaced closely adjacent the orifice therethrough. The inner group of projections coacts with the resilient flow control member as it deflects axially to provide and maintain a predetermined bypass flow characteristic across a wide range of differential pressures.

Description

Q~

B~C~GROUND OF ~E }NVEN~ION

In flow control devices of the orifice restriction type constant flow rates are achieved when the pressure drop across the device is sufficient to permit fluid inertial effects to substantially restrict flow rates regardless of further increases in upstream fluid pressure. Flow control devices of this type find a wide variety of uses ranging from controlling flow rates in shower heads to applications in which irrigation line flow rateS must be controlled to conserve water usage.
A performance aspect associated with prior art devices is that the flow rate increases at a rate directly proportional to the pressure drop across the device until a relatively large pressure differential is reached in which fluid inertial effects limit flow. Some flow control devices have employed a bypass feature partially compensating for this aspect, but experience has shown that the bypass feature becomes inoperative at higher pressure differentials resulting in a mar~ed discontinuity in the flow rate. The inability of prior art bypass techniques to overcome this shortcoming has been due primarily to the difficulty of controlling and maintainirg bypass flow passages around the outer diameter and periphery of the downstream face of the control member where pressure and viscous forces are most severe, and has resulted in excessive control member deflection.

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The present invention overcomes the above-described disadvantages of the prior art by substantially reducing deviations from a constant flow rate and provides.
sufficiently effective control of the flow such that, during low pressure differential conditions, a constant flow rate is more closely maintained.
According to one aspect of the present invention, there is provided a method for fluid flow in a conduit having an inlet and an outlet at a substantially constant rate over an intended range of varying fluid inlet pressures.
The method includes flowing the fluid through an enlarged section in the flow area of the fluid conduit intermediate the inlet and outlet and disposing a resilient washer trans-versely of the flow in the section and spacing the outer periphery thereof from the inner wall of the section to permit bypass flow therebetween. The downstream face of the washer is maintained spaced from the wall of the enlarged section of the conduit such that the bypass flow is not blocked as the washer deflects transversely under increased forces of increased inlet pressure, thereby maintaining the bypass flow additive to the central flow through the washer at all inlet service pressures.
According to another aspect of the present invention, there is provided a flow control washer operative upon placement in a fluid conduit having an inlet and outlet to permit primary flow therethrough and bypass flow t~erearound and to maintain the flow between the inlet and outlet substantially constant throughout a range of intended inlet service pressures. The washer has a primary flow aperture therethrough with means defining in cooperation ~ith the fluid conduit at least one axial flow passage extending along the outer periphery of the washer from the p -2-~ ) upstream face to the downstream face thereof. Spacing means is disposed on the downstream face of the washer, the spacing means being operative, upon the washer being subjected to an inlet pressure less than a first predeter-mined value, to provide a predetermined maximum level of bypass flow and the spacing means being operative upon the washer being subjected to inlet pressures greater than the first level by a predetermined amount, to maintain the bypass flow at a reduced predetermined minimum level so that the washer maintains substantially constant flow throughout the pressure range.

2a-ll llOOOi3 BRIEF DESCRIPTION OF T~E DRAWINGS

FIGVRE 1 is an axial cross section of the invention in operation under low differential pressure conditions.
FIGURE 2 is an axial view similar to Figure l taken S through section indicating lines 2-2 showing the downstream face of the control member.
FIGURE 3 is a cross-sectional view of the invention similar to Figure l illustrating maximum deflection of the control member resulting from high differential pressure conditions.
FIGURE 4 is an elevation view in cross section of a second embodiment of the invention.
FIGURE 5 is a graph of flow rate versus pressure differential for a flow control device of the present invention and also a typical flow control device lacking bypass control.

DETAILED DESCRIPTION

Referring now to Figure l, a flow control device is indicated generally by reference numeral 10. An upstream housing section 12 and a downstream housing section 14 are joined and fluidly sealed together by any convenient expedient compatible with the material used for fabrication. Where plastic has been used for sections 12 and 14, sonic welding has been found to be particularly satisfactory. Upstream housing section 12 has an inlet passageway 16 formed in a tubular portion 18 thereof.
Downstream housing section 14 has an outlet fluid passageway 18 formed in a tubular portion 22 thereof. An intermediate flow chamber 23 is defined by housing sections 12 and 14 and is bounded by an upstream wall 24, a downstream wall 25, and a cylindrical bore having an internal diameter 26. A disc-shaped flow control member 27 having a centrally located metering orifice 36 is disposed within flow chamber 23 and is formed of a resilient material, preferably an elastomer. The control member has a plurality of lobes or extensions projecting radially outwardly from the outer periphery thereof in preferably circumferentially equally spaced arrangement, a typical one of which is indicated by reference numeral 28. Flow chamber internal diameter 26 is appropriately sized for slidably maintaining the flow control member 27 transversely in a desired position. The circumferential spaces between individual lobes 28 and internal diameter 26 of the fluid chamber define fluid passageways which function in a manner that will be subsequently described. The flow control member 27 has a preferably flat upstream surface 32 and a pr~ferably concave or dished downstream surface 34. A plurality of pads 35 are formed on upstream surface 32 and serve to space the control member from upstream wall 24.
With continued reference to Figure l,and additionally Figure 2, projections 38, 40 and 42 are formed around the outer periphery of downstream surface 34 while an inner group of projections 46, 48 and 50 are formed near metering orifice 36 and preferably circumferentially equally spaced thereabout. The ll~Qi3 inner group of projections are spaced radially outward from orifice 36 an amount sufficient to clear the inner diameter of outlet passage 20. With continued reference to Figure 1, the outer group of projections 38, 40 and 42 project axially from . 5 - downstream s~face 34 . a pxedetermined amount greater than the axial projection of the inner group of projections 46, 48 and.
S0 such that the flow control member, while in a substantially unflexed condition as illustrated in Figure 1, has only the .
: outer projections 38, 40 and 42 thereof contacting the downstream wall of the fluid chamber.
By way of illustration, a typical configuration for a `
flow control element rated at approximately 0.80 gallons per minute is characterized as having a metering orifice with an internal diameter of 0.097 inch (2.46 mm), an outer diameter of.
0.500 inch (12.7 mm), a thickness of 0.125 inch (3.17 mm), an axial concavity in the downstream face to a depth of 0.014 inch (0.35 mm), an axial extension beyond the downstream face for the outer group of projections of 0.008 inch (0.20 mm), and an axial extension beyond the downstream face, measured at the point of maximum concavity, for the inner group of projections of 0.014 inch (0.35 mm). The parameters outlined above can be used to formulate relationships respecting flow control member configura-tion. For example, the ratio of outer diameter to axial thickness controls the transverse flexibility for a given

2~ material. This ratio R is held substantially constant and a particular suitable ratio for elastomeric material has been ll~Q ~;~

found to be 5:1, however, other ratios may be employed for other materials. For a given flexibility of the control member the response of the bypass flow component can be established by the - spacing of the downstream face, at the inner group of projections from the downstream wall and also the spacing from the ends of the inner group of projections from the downstream wall. In the presently preferred practice this spacing of the downstream face from the downstream wall may be ex~ressed as a percentage of the metering orifice diameter and a particular satisfactory -10 value for elastomeric material has been found to be 20 percent, however, it will be understood other values may be appropriate for other materials. In a similar fashion the spacing of the ends of the inner group of projections, in the axially relaxed condition, from the downstream wall may be expressed as a percentage of the metering orifice diameter and a particular satisfactory value for elastomeric material has been found to be 8 percent; however, it will be understood other values may be appropriate for other materials. By altering the ratio R, the amount of axial deflection for a given pressure differential can be adjusted to achieve, in cooperation with the inner group of projections and depth of concavity, a bypass flow response to suit varying application requirements.
In operation, fluid flow enters inlet fluid passageway 16 and, when under relatively low pressure differentials as, for example, of the order of 1 - 2 psi as measured across the inlet and outlet passages, ~ollows a path indicated by the black arrows in Figure 1. Axial deflection of the flow control member at low pressure differentials is minimal and the control mem~er assumes a shape substantially as shown in Figure 1. Even at such low pressure differentials the fluid forces are, however, suffi-cient to thrust the flow control member against downstream wall 25. A portion of the total fluid flow carried by inlet passage 16, designated as primary flow, flows directly through metering orifice 36 and into outlet passageway 20. That portion of the flow not passing through metering orifice 36, designated as bypass flow, follows a path radially outward between the upstream surface 32 of the flow control member and the upstream wall 24 of flow chamber 23. Upon reaching the wall of the flow chamber at internal diameter 26, the fluid then flows through the spaces between lobed extensions 35 and in a direction parallel to flow through metering orifice 36. Upon reaching the downstream wall 25 of the flow chamber the fluid enters the space between the downstream surface 34 and the downstream wall 25 of the flow chamber. The concavity of downstream surface 34 of the control member serves to offset the reduction in cross-sectional flow area as the fluid approaches the center of the control member.
The bypass flow component combines with the primary flow component exiting from the metering orifice whereupon flow continues on through outlet fluid passage 20. The function of the bypass flow feature is to permit a greater volume of bypass fluid to flow through the device than would be possible solely through the metering orifice under conditions of low differential pressures.

. Il 11~ 3 As the upstream line pressure increases, the flow rate through the bypass path described above increases accordingly, during which time the flow control member is axially deflected by the pressure differential existing across the flow member and also the forces due to fluid viscosity. The axial deflection, which is maximum near the center of the flow control member, continues to increase until the inner group of projections 46, 48 and 50 abut downstream wall 25. The axial projection of the inner group of projections, plus the amount of concavity, is chosen to achieve a predetermined bypass flow characteristic which, when added to the primary flow through the metering orifice 36, results in substantially constant flow rate across a wide range of pressure differentials. It should be noted that, a the flow rate increases, the contribution to total flow required from the bypass component becomes diminished. However, it has been found desirable to maintain a predetermined amount of bypass flow throughout the full range of service pressure differentials in order to prevent collapse of the flow control member against downstream wall 25 and a discontinuity in the resultant flow rate. By placing the inner projections 46, 48 and 50 near the point of maximum axial deflection of the flow control member, significantly improved control over the bypass flow component can be achieved by limiting axial deflection of the flow control member to a predetermined amount. A graphical representation of the bypass flow component for a flow control member having this control feature blotted as a function of pressure drop would be characterized by a substantially linear increase to a given maximum followed by a controlled drop-off to a given minimum.
Thus, an abrupt closing-off of the bypass component which would result in a sudden drop in the resultant flow rate is avoided.

11~ 3 The above-described performance aspects are illustrated in Figure 5 by a graph of flow rate versus pressure differential as measured across the inlet passage to the outlet passage.
Curve "A" represents the resultant flow rate of the invention incorporating the controlled bypass feature disclosed above while curve "B" represents resultant flow for a control device without controlled bypass flow. In the region from 0 psi to approximately 3 psi both devices permit flow to increase at a substantially linear rate until maximum values are reached.
During this stage of operation, axial deflection of each device has been minimal. Beyond the point of maximum flow rate, however axial deflection for both devices increases rapidly causing a reduction in cross-sectional flow area along the bypass flow path as indicated in the region from 3 psi to 5 psi. The abrupt reduction in flGw rate evidenced by curve "B", over 25 percent, results from closing-off of the bypass passage. In contrast, curve "A" drops off less than 6 percent, a significant difference in performance from curve "B." Beyond 5 psi differential pressure the resultant flow rate of curve "A" is substantially constant. The remainder of curve "B" beyond 5 psi differential exhibits a gradual increase in flow occurring through a central orifice.
Figure 3 illustrates the flow control member under relatively high differential pressure conditions at which maximum axial deflection has occurred and where furthQr axial deflection is prevented by the abutment of the inner group of projections 46, 48 and 50 against the downstream wall of the fluid chamber.

. Il ll~g;iQ~3 Referring now to Figure 4, there is illustrated a second embodiment of the invention in which the outer and inner group of projections are integrally formed on the downstream wall of downstream housing section 14, the embodiment of Figure 4 being otherwise similar to the embodiment of Figure 1. Reference numerals 54 and 56 designate typically two of a plurality of axially extending circumferentially spaced outer projections while reference numerals 58 and 60 designate a typical pair of similarly arranged inner projections located near the central metering orifice. In the preferred practice of the invention at least three outer and inner`projections are employed in order to maintain satisfactory alignment and spacing of the flow control member with respect to downstream wall 25. A greater number, however, may be utilized where required by fluid flow rates and viscosities.
The operation of the second embodiment of the invention is similar to the operational characteristics hereinabove described for the first embodiment.
The embodiments of the invention as shown and described above are representative of the inventive principles as stated herein. It is to be understood that variations and departures can be made from the embodiments as shown without, however, departing from the scope of the appended claims.

Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of controlling fluid flow in a conduit having an inlet and outlet at a substantially constant rate over an intended range of varying fluid inlet pressures comprising the steps of:
(a) flowing said fluid through an enlarged section in the flow area of the fluid conduit intermediate said inlet and outlet;
(b) disposing a resilient washer transversely of the flow in said section and spacing the outer periphery thereof from the inner wall of said section to permit bypass flow therebetween; and (c) maintaining the downstream face of said washer spaced from the wall of said enlarged section of said conduit such that said bypass flow is not blocked as the washer deflects transversely under increased forces of increased inlet pressure, thereby maintaining said bypass flow additive to the central flow through said washer at all inlet service pressures.

2. A flow control washer operative upon placement in a fluid conduit having an inlet and outlet, to permit primary flow therethrough and bypass flow therearound and to maintain the flow between said inlet and outlet sub-stantially constant throughout a range of intended inlet service pressures as having said washer characterized as having:
(a) a primary flow aperture therethrough;
(b) means defining in cooperation with said fluid conduit at least one axial flow passage extending along the outer periphery of said washer from the upstream face to the downstream face thereof; and (c) spacing means disposed on the downstream face of said washer, said spacing means being operative, upon said washer being subjected to an inlet pressure less than a first predetermined value, to provide a predetermined maximum level of bypass flow and said spacing means being operative upon said washer being subjected to inlet pressures greater than first level by a predetermined amount, to maintain said bypass flow at a reduced predetermined minimum level, whereby said washer maintains substantially constant flow throughout said pressure range.

3. A device as defined in Claim 2, wherein the ratio of the transverse dimension across the outer periphery of said washer to its thickness in the direction of axial fluid flow is in the range of 4-8:1.

4. A device as defined in Claim 2, wherein the ratio of the internal diameter of said primary flow aperture to the axial spacing of said washer downstream face from said outlet fluid conduit as measured closely adjacent said primary flow aperture is 5:1.

5. A washer for use in an enlarged section of a fluid conduit having inlet and outlet operative to maintain substantially constant flow therethrough by controlling primary and bypass flow characterized in that the washer has:
(a) a primary flow aperture therethrough;
(b) a plurality of projections circumferentially spaced about the outer periphery and extending generally radially outwardly therefrom;
(c) a downstream face having first portions configured so as to define in cooperation with said fluid conduit at least one first radial flow passage from the outer periphery to the primary flow aperture; and (d) said downstream face having second portions configured so as to define in cooperation with said fluid conduit at least one second radial flow passage, said second portion being disposed radially intermediate said first portions and said primary flow aperture wherein upon said washer being subjected to inlet pressures below a first predetermined level said first portions are operative to limit bypass flow between said radial projections and, upon said washer being subjected to inlet pressure greater than a second predetermined level higher than said first level, said washer is deflected transversely such that said bypass flow is reduced and said second portions are operative to prevent blockage of said bypass flow throughout a full range of intended service pressure differentials across said device.
6. A device for controlling fluid flow, comprising:
(a) housing means defining a fluid chamber, said housing means further defining inlet and outlet fluid passageways communicating with said fluid chamber, said fluid chamber having a downstream wall adjacent said outlet passageway, said downstream wall extending generally trans-versely with respect to the flow direction of said outlet passageway;
(b) a resilient control member having a metering orifice therethrough and disposed within said fluid chamber and having the outer periphery thereof sized and configured so as to define in cooperation with said chamber wall a bypass fluid passageway therebetween, said control member having a downstream surface with a portion thereof defining in cooperation with said downstream radial flow passage, said control member being disposed in said fluid chamber such that said downstream surface is adjacent said outlet

Claim 6 cont'd fluid passageway;
(c) first means for permitting flow exiting from said bypass passageway to flow in a substantially radially inward direction across said downstream surface of said control member, said first means being located between said downstream surface and said downstream wall and spaced closely adjacent the outer periphery of said control member; and (d) second means for substantially controlling said flow exiting said first means, said second means being located between said downstream wall and said down-stream surface and spaced inward radially from said first means, said second means being operable to permit axial deflection of said control member and reduction of flow in said bypass, said second means being further operable at pressure differentials above a predetermined level to sub-stantially prevent axial deflection of said control member and substantially prevent further reduction of flow in said radial flow passage for maintaining substantially constant-rate flow through said device throughout a full range of intended service pressure differentials across said device.

7. A device as defined in Claim 6, wherein said first means includes a plurality of radial grooves located outward radially in said downstream surface.

8. A device as defined in Claim 6, wherein said first means includes a plurality of projections extending from said downstream surface and located outward radially along said downstream surface.

9. A device as defined in Claim 6, wherein said first means includes a plurality of projections extending from said downstream wall.

10. A device as defined in Claim 6, wherein said second means includes a plurality of projections extending from said downstream surface, said projections located inward radially from said first means and spaced closely adjacent the edge of said metering orifice.

11. A device as defined in Claim 6, wherein said second means includes a plurality of projections extending from said down-stream wall and spaced thereon for contacting said downstream surface closely adjacent the edge of said metering orifice.

12. A device as defined in Claim 6, wherein said control member is cylindrically shaped having an outer diameter substant-ially greater than its thickness with an upstream surface sub-stantially flat and wherein said recessed surface is substantially concave, said control member being formed from an elastomeric material.