GB2163557A - Flow meter including bypass valve assembly - Google Patents

Abstract

A pressure relief valve 51 in a flow meter allows excess flow to bypass the flow sensor 34 and pass directly to outlet 38. Thus the flow sensor can accurately measure low flows and not be damaged by high flows. At low flows the orifice plate 32 carried by piston 16 is urged upwards against spring 37 and operates a pointer 18. Central member 34 is tapered. <IMAGE>

Description

SPECIFICATION Flow meter bypass valve assembly The invention relates generally to valve assemblies and, more particularly, to a bypass valve assembly for a fluid flow meter.

There are a number of different types of fluid flow meters. In general, however, fluid flow meters comprise a housing having an inlet, an outlet and a fluid passage formed through the housing for fluidly connecting the inlet to the outlet. A flow responsive member is mounted within the housing in the fluid passage so that the position of the flow responsive member varies in accordance with the fluid flow rate through the flow meter. Indicator means provide an external signal of the position of the flow response member and thus of the fluid flow rate.

Flow meters are conventionally designed to operate over a predetermined range of fluid flow rates. Furthermore, if the maximum fluid flow rate for the flow meter is exceeded, particularly by a large amount, the flow meter is often damaged thus requiring expensive repair and/or replacement.

For many applications, however, the user of the flow meter is desirous only of determining when the fluid flow rate falls below a predetermined and relatively low flow rate. Such low flow rates are typically indicative of a clogged system or other malfunction of the fluid system. At the same time, however, the flow meter must be capable of operating under relatively high fluid flow rates without damaging the flow meter although the actual flow rate above the predetermined minimum flow rate is unimportant.

For such fluid applications, the use of a flow meter having a relatively high fluid flow range has not proven wholly satisfactory. First, flow meters with high flow ranges are relatively expensive in construction and thus uneconomical for the user who desires to determine only when the flow rate falls below a predetermined minimum amount. Secondly, the accuracy of many flow meters decreases proportionately with the range of fluid flow rates of the flow meter. Thus, a flow meter with a very high flow range is incapable of accurately measuring relatively low fluid flow rates.

An object of the invention is to provide a bypass valve assembly which overcomes the above-mentioned disadvantages.

In brief, the bypass valve assembly of the invention is designed for use with a conventional fluid flow meter. Such a fluid flow meter comprises a housing having an inlet, an outlet and a fluid passage formed through the housing for fluidly connecting the inlet to the outlet. A flow responsive member is positioned within the fluid passage and the position of the flow responsive member varies in dependence upon the fluid flow rate through the flow meter passage. An indicator provides an external signal of the position of the flow responsive member and thus of the fluid flow rate.

According to the invention a fluid flow meter of the type having a housing, an inlet, an outlet, fluid passage means formed in said housing fluidly connecting said inlet to said outlet and a flow rate responsive member contained in said fluid passage means includes a bypass valve assembly comprising a body; a fluid passageway formed in said body, said fluid passageway having an inlet end and an outlet end; means for securing said body to said housing so that said inlet end is open to said flow meter inlet and said outlet end is open to said fluid passage means between said flow rate responsive member and said flow meter outlet; a valve member movable between an open position in which said valve member established fluid communication between the ends of said passageway and a closed position in which said valve member prevents fluid flow between said ends of said passageway and means for moving said valve member to said closed position when the fluid flow into said flow meter inlet is less than a predetermined rate.

The body of the bypass valve assembly may comprise a tube open at one end and secured to the housing so that the open end of the tube is aligned with and open to the flow meter inlet. Consequently, influent to the flow meter inlet would normally pass into the interior of the tube. At least one and preferably a plurality of radial ports may be formed through the tube at a position axially spaced from its open and and open to the interior of the tube. In addition, the radial port or ports are in fluid communication with the flow meter passage at a position between the flow responsive member and the flow meter outlet.

The valve member may be longitudinally slidably mounted within the interior of the tube and is normally urged towards a closed position by a spring wherein the valve member extends across the interior of the tube in between the radial ports or ports and the open end of the tube. Consequently, in its closed position, the valve member prevents fluid flow through the tube and instead directs the influent to the flow meter inlet through the flow meter passage. When the valve member it in its closed position, the flow meter operates in its normal fashion and the true fluid flow rate through the fluid meter is displayed by the flow meter indicator means.

When the flow rate of the influent exceeds a predetermined amount, the valve member compresses against the force of the spring thus establishing fluid communication from the open end of the tube and to the radial port or ports. In doing so, a portion of the influent bypasses directly from the flow meter inlet and to the flow meter outlet. The valve mem ber will remain in its open position as long as the flow rate to the flow meter inlet exceeds the predetermined flow rate amount.

The invention also includes a bypass valve assembly for use in a fluid flow meter as set out hereinbefore.

A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which: Figure 1 is a sectional view illustrating a flow meter utilizing a preferred embodiment of the bypass valve assembly of the present invention; Figure 2 is a cross-sectional view of the preferred embodiment of the bypass valve assembly and enlarged for clarity; Figure 3 is a cross-sectional view taken substantially along line 3-3 in Fig. 2; and Figure 4 is a partial sectional view similar to Fig. 1 but illustrating the bypass valve assembly in its open position.

With reference first to Fig. 1, a flow meter 10 is thereshown having a housing 12 which defines an interior cylindrical chamber 14. A flow responsive member 16, such as a piston, is longitudinally slidably mounted within the chamber 14 while indicating means 18 provide an exteriorly visible signal of the axial position of the flow responsive member 16 within the chamber 14.

An inlet 20 on the housing 12 fluidly communicates through passageways 22, 24 and 26 to one side of the flow responsive member 16. The flow responsive member 16 includes a radial passageway 28 and an interior bore 30 which, together, establish fluid communication from the passageway 26 and to a ported plate 32 carried by the flow responsive member 16.

The ported plate 32 cooperates with a tapered rod 34 to form an opening 35 between the interior bore 30 of the flow responsive member 16 and an upper subchamber 36 formed above the member 16. The area of the opening 35 varies with the axial position of the flow responsive member 16 and a spring 37 urges the member 16 in the direction opposite from the fluid flow through the opening 35. An outlet 38 on the flow meter housing 12 is open to the subchamber 36.

The flow meter passageways 22, 24 and 26 together with the cross passage 28, bore 30 and opening 35 form a fluid passage for fluidly connected the flow meter inlet 20 to the outlet 38. Consequently, the flow responsive member 16 is fluidly mounted in series with the fluid passage means so that fluid flow from the inlet 20 and to the outlet 38 normally flows through the bore 30 of the flow responsive member 16 and through the opening 35. The position of the flow responsive member 16 within the housing chamber 14 is thus indicative of the flow rate through the flow meter 10 and this flow is displayed exteriorly of the flow meter housing 12 by the indicator means 18.

The foregoing description of the flow meter 10 is by way of example only and is presented only for clarity and completeness. As will become shortly apparent, the bypass valve assembly according to the present invention can be used with flow meters of different constructions and utilising different types of flow responsive members.

With reference now to Fig. 2, a preferred embodiment of the bypass valve assembly 42 of the present invention is thereshown and comprises a body 44 which is tubular and cylindrical in shape. The body 44 is open at one end 46 and has an axial bore 48 formed through its other end 50. The body 44 thus forms an interior cylindrical chamber 52 and a plurality of circumferentially spaced radial ports 51 are formed through the body 44 and open to the chamber 52 at a position axially spaced from the open end 46 of the body 44.

A disc shaped valve member 54 having an axial throughbore 56 is slidably mounted within the body chamber 52. The outside diameter of the valve member 54 is substantially the same or slightly less than the diameter of the body chamber 52 so that the valve member 54 extends substantially entirely across the body chamber 22.

A cylindrical rod 58 having an enlarged head 60 at one end is inserted through the valve member bore 56 and the bore 48 at the end 50 of the body 44 so that the enlarged head 60 is positioned between the valve member 54 and the open end 46 of the body 44. The rod 58 is dimensioned so that, with the valve member 54 positioned between the open end 46 of the body 44 and the radial ports 51, a portion 62 of the rod 58 extends outwardly from the end 50 of the body 44. A compression spring 64 is contained within the body chamber 52 between the valve member 54 and the end 50 of the body 44 and urges the valve member 54 toward the open end 46 of the body 44. A retainer 66 is secured to the rod portion 62 to limit the travel of the valve member 54 to a position in between the ports 51 and open end 46 of the body 44.

With reference now to Figs. 1 and 2, the body 44 includes an externally threaded portion 68 adjacent the open end 46 of the body 44. This threaded portion 68 threadably cooperates with an internally threaded bore 70 (Fig. 1) in the flow meter housing 12 and the bore 70 is both fluidly open to and aligned with the flow meter inlet 20. With the bypass valve assembly 42 secured to the flow meter housing 12 as shown in Fig. 1, the influent to the flow meter inlet 20 will impact upon the valve member 54. At the same time, the radial ports 51 are open to the subchamber 36 and thus open to the flow meter fluid passage at a position between the flow responsive member 16 and the outlet 38.Furthermore, with the bypass valve assembly 42 secured to the flow meter housing 12, the bypass valve assembly chamber 52 forms a passageway with the open end 46 of the chamber 52 forming an inlet end of the passageway and the radial ports 51 forming an outlet end of the passageway.

With reference to Fig. 1, in operation and during relatively low fluid flow rates into the housing inlet 20, the compression spring 64 maintains the valve member 54 in a closed position, i.e., between the open end 46 of the body 44 and the radial ports 51. In its closed position, the valve member 54 prevents fluid flow through the bypass valve assembly 42 so that all of fluid flow into the housing inlet 20 passes through the flow meter passage 22. In doing so, the fluid flow axially displaces the flow responsive member 16 which in turn actuates the indicator means 18 to display true fluid flow rate through the flow meter 10.

With reference now to Fig. 4, when the fluid flow rate of the influent to the flow meter 10 exceeds a predetermined rate, as determined by the helical spring 37, the bypass valve member 54 retracts within the body chamber 52 to its open position. In its open position, the valve member 54 uncovers the radial ports 51 thus establishing fluid communication between the open end 46 of the body 44 and the radial ports 51. In its open position, the bypass valve assembly 42 fluidly connects the flow meter inlet 20 to the flow meter outlet 38, thus bypassing flow responsive member 16. During the bypassing condition, the flow rate indicated by the indicator means 18 will not be accurate. However, for many flow meter applications, the user is desirous only of detecting when the flow rate falls below a predetermined rate while the actual measurement of the flow rate above that predetermined rate is unimportant.

Claims (10)

1. A fluid flow meter of the type having a housing, an inlet, an outlet, fluid passage means formed in said housing fluidly connecting said inlet to said outlet and a flow rate responsive member contained in said fluid passage means, the fluid flow meter including a bypass valve assembly comprising a body; a fluid passageway formed in said body, said fluid passageway having an inlet end and an outlet end; means for securing said body to said housing so that said inlet end is open to said flow meter inlet and said outlet end is open to said fluid passage means between said flow rate responsive member and said flow meter outlet; a valve member movable between an open position in which said valve member establishes fluid communication between the ends of said passageway and a closed position in which said valve member prevents fluid flow between said ends of said passageway and means for moving said valve member to said closed position when the fluid flow into said flow meter inlet is less than a predetermined rate.

2. A fluid flow meter as claimed in Claim 1 wherein said body comprises a tube open at one end and forming an interior chamber, said tube being connected to said housing so that said open end of said tube is open to said flow meter inlet.

3. A fluid flow meter as claimed in Claim 2 wherein said passageway comprises at least one radial port formed through said tube and open to said interior chamber at a position axially spaced from said open end of said tube.

4. A fluid flow meter as claimed in Claim 3 and comprising means for longitudinally slidably mounting said valve member in said interior chamber and wherein in said closed position said valve member extends across said interior chamber between said radial port or ports and said open end of said tube.

5. A fluid flow meter as claimed in Claim 4 wherein said slidable mounting means comprises a rod secured at one end to said valve member and having its other end slidably mounted in a bore at the other end of said tube.

6. A fluid flow meter as claimed in any preceding claim wherein the means for moving said valve member comprises a compression spring entrapped between said valve member and the other end of said body.

7. A fluid flow meter as claimed in any one of Claims 2 to 5 wherein said tube includes threads at said open end of the tube and wherein said threads cooperate with a threaded portion of said flow meter housing, said threaded portion being coaxial with said inlet so that said body is axially aligned with the fluid flow into said flow meter inlet.

8. A bypass valve assembly for use in a fluid flow meter as claimed in any of the preceding claims.

9. A fluid flow meter substantially as described herein and shown in the accompanying drawings.

10. A bypass valve assembly for use in a fluid flow meter as described herein and shown in the accompanying drawings.