GB2162326A - Flow indicator - Google Patents

Abstract

A flow indicator has a flap (22) pivotally mounted across a fluid inlet (14), the flap being shaped and arranged so that the fluid flow therepast is turbulent, and causes the flap to oscillate in a random manner. The flap is viewed through a window. A plurality of flaps may be provided. The or each flap is preferably shaped to be concave on one side and convex on the other. The flap also has a surface on the leading side of the pivot axis against which the fluid flow reacts to oppose the tendency to pivot mentioned above. <IMAGE>

Description

SPECIFICATION Flow indicator Conventional flow indicators can be of the flap, sighting and spinner types. Such indicators have a flow chamber with a flow inlet to said chamber. In the flap type, a flap is hinged to lie in a rest position across the mouth of the flow inlet where fluid enters the chamber from the flow inlet. Pressure of fluid entering the chamber pivots the flap away from its rest position and the operative position of the flap gives an indication of the rate of flow of fluid. The flap is biased by gravity or other means towards its rest position when the fluid flow reduces. The flow around the flap is as nearly streamline as possible, so that the flap remains stationary for uniform flow, enabling a reading of the fluid flow to be made from the flap position.

The sighting type of flow indicator has a transparent window in the chamber so that flow entering the chamber from the inlet can be observed. This type of indicator is not useful with fluids which do not contain entrained foreign material and which fill the entire chamber.

In the spinner type of indicator, the flow of fluid from the flow inlet impinges on the spinner and caused it to rotate. The rotation of the spinner is observed through a window or caused to provide an indication remote from the chamber, thus giving a measure of the fluid flow.

The present invention is a modification of the sighting type of indicator and extends the use of that type of indicator to fluids which do not have foreign material entrained and which completely fill the chamber. It provides a fluid flow indicator comprising a chamber having an inlet and an outlet for the flow of fluid therethrough, and a flap member pivotally mounted between said inlet and said outlet and asymmetrically shaped about a plane containing said axis. Such an indicator is disclosed in United States Patent Specification 4092859, where the two wing-like elements extend alongside each other and one is pivotally mounted so as to oscillate at a frequency proportional to the fluid flow rate. The fluid flow rate can therefore be indicated from a measurement of the oscillation frequency.The present invention differs from such a device in having a viewing window for viewing the flap member and further by one or both of the following features. The first of the features is that there are a plurality of flap members arranged side by side across the fluid flow path. As the fluid flow varies across the width of the path, the flap members will oscillate at different rates and so will give a better indication through the viewing window that fluid flow is taking place.The other feature is that the flap member has a first side and a second side opposite the first side, said first side being concave and/or said second side being convex so that the fluid flow tends to pivot the member away from the first side towards the second side, the flap member also having a surface on the leading side of the pivot axis against which fluid flow reacts to oppose the tendency to pivot aforementioned.

An example of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a side elevation of a first fluid indicator, Figure 2 is a transverse section through the indicator of Fig. 1, Figure 3 is a side elevation of a second fluid indicator, and Figure 4 is a transverse section through the indicator of Fig. 3.

The indicator of Fig. 1 has a conventional flow chamber 11 formed with a pair of transparent windows 1 2 of toughened glass on respective opposite sides. The windows 1 are retained by covers 1 3. As can be seen from Fig. 1, a fluid inlet conduit 1 4 extends into the chamber, having a mouth 1 5 which subtends approximately 120 at the centre of the chamber which has a circular section in the plane of Fig. 1. As so far described, the indicator resembles a sighting type of indicator. Close to the mouth 15, the inlet conduit 14 is drilled to receive a spindle 21 on which are freely pivoted a plurality of flap members in the form of fingers 22.The fingers 22 are asymmetrical about the axis of spindle 21 so that in no-flow conditions they tend to hang below the spindle, and they are also asymmetrical about their central longitudinal axis as seen in Fig. 1, the upstream side of the finger 22 (relative to the direction of flow which is from left to right in Fig. 1) being concave and the downstream side being convex. The bodies of the fingers 22 are spaced from each other by bosses as illustrated in Fig. 2, but other spacer means could be provided as desired. There are preferably at least two fingers provided on the spindle and as shown in Fig. 2 a finger is provided on the spindle outside the width of the inlet 1 4 besides the fingers mounted across the section of the inlet.In order that such fingers outside the inlet 1 4 will be properly affected by the flow, an aperture 23 is formed in the side of the inlet near its mouth so that there will be a flow of fluid past such fingers outside the inlet.

It will be seen from Fig. 2 that the spindle lies across the section of the inlet 1 4 and in this particular example across its diameter.

The fingers 22 individually and in concert cover only a small proportion of the section of the inlet. These conditions are so different from the uniform flow and coverage of the flap-type indicator that turbulent flow is set up and an indication of flow is given, not neces sarily by the position of a finger 22, because this is rapidly changing due to the turbulent flow, but by the oscillatory movement of the fingers 22 as viewed through the windows 12.

The indicator of Figs. 3 and 4 resembles that already described in that the flow chamber 11 has a pair of transparent windows 12 retained by covers 1 3. The fluid inlet in this indicated does not protrude into the chamber 11, but the fluid inlet conduit 31 ends at the cylindrical surface of the flow chamber. On either side of the conduit, a lug 32 extends into the chamber 11 to support the spindle 21 for three fingers 33. The fingers 33 have the same longitudinal sections of the fingers 22 already described but are bifurcated at the spindle 21, as can best be seen in Fig. 4.

This construction allows the outside fingers 33 to straddle the lugs 32, thus allowing the outside fingers to lie close to the windows 1 2 while extending to a position in line with the conduit 31 so as to be affected by the flow of fluid through the chamber 11. The centre finger has the same longitudinal section as the others, but is reversed with the respect of the outside fingers so that its concave face faces the same way as the convex faces of the outer fingers and its convex face faces the same way as the concave faces of the outside fingers. The centre finger is aligned with the centre of the inlet conduit 31 and so is most sensitive to fluid flow although its visibility from the windows 1 2 is more likely to be reduced by cloudy fluid.The fingers 33 have bosses 34 around the spindle bore to keep the remainder of the fingers spaced from each other and from the windows 1 2. The fingers are brightly coloured for maximum visibility within the fluid. The reversed centre finger will be affected differently by the fluid flow and so will both increase the turbulence in the chamber and increase the visible indication of fluid flow from the different forces acting upon it due to the fluid flow through the chamber.

It will be seen from Figs. 1 to 3 that the finger 22 has a tail extending down stream from the pivot axis to spindle 21, one side of the tail being convave and the other convex.

In streamline flow, the tail tends to rotate anticlockwise as seen in Fig. 1 about the spindle 21 since the flow tends to react more strongly against the concave side than the convex side.

To counteract this rotation, the leading edge of 24 of the finger 22, on the opposite side of the spindle 21 from the tail, is made plane and approximately at right angles to the general length of the tail. The leading edge 24 extends asymmetrically of the spindle 21, and to a greater extent on the convex side of the tail rather than the concave side, so that the reaction of the fluid flow tends to rotate the finger 22 clockwise as seen in Fig. 1, opposing the tendency to rotate in the opposite direction caused by the reaction of the fluid flow on the concave and convex surfaces of the finger.With the turbulent flow (as distinct from streamline flow) encountered in practice, the balance of these forces is disturbed and the flap member oscillate indicating that fluid flow is taking place to an observer of the finger through the viewing window 1 2. This indication is greater when a plurality of fingers 22 are provided since fluid flow conditions differ across the width of the conduit 1 4 and the different fingers oscillate at different rates, and the affect is even more marked when some fingers are reversed. The shape of the finger does however enable the object one aspect of the invention to be achieved with only a single finger.

The illustrated apparatus can be mounted in any orientation, besides the illustrated orientation with the axis of the inlet conduit 14 and 31 horizontal. The axis could for example be vertical, with the inlet conduit 14 entering the chamber 11 from above or below. The effect of gravity on the fingers 22 is of no importance, since the flow indication is generated by the turbulent flow.

The fingers can be of any convenient material, but the desired properties of lightness, durability and a shape to create turbulent flow indicates that moldable plastics materials are the most suitable. The mounting of fingers freely pivotable about an axis gives far superior durability than strips of tape which have previously been attached in fluid chambers to indicate flow by their random motion. Such tapes have been found to break off after a period of use, creating difficulties downstream of the indicator. The three finger members of the second embodiment have the same shape, but different flow conditions are set up by the reversal of the centre finger member.

The embodiment of Figs. 3 and 4 may have more than 3 fingers. When there is more than one central finger, some or all may be reversed in relation to the outer fingers.

Claims (8)

1. A fluid flow indicator comprising a chamber having an inlet and outlet for the flow of fluid therethrough, a flap member pivotally mounted between said inlet and said outlet and asymmetrically shaped about a plane containing said axis, the flap member having a first side and a second side opposite said first side, said first side being concave and/or said second side being convex so that the fluid flow tends to pivot the member away from the first side towards the second side, the flap member also having a surface on the leading side of the pivot axis against which fluid flow reacts to oppose the tendency to pivot aforementioned, said chamber having a window for viewing said flap member.

2. An indicator as claimed in Claim 1 comprising a plurality of said flap members arranged side-by-side across the flow path and mounted about the same pivot axis.

3. A fluid flow indicator comprising a chamber having a fluid flow path with an inlet and an outlet therefor, a plurality of flap members arranged side-by-side across the flow path and pivotally mounted between said inlet and said outlet and asymmetrically shaped about a plane containing said axis, said chamber having a window for viewing the flap members.

4. An indicator as claimed in Claim 3 wherein said flap member has a first side and a second side opposite said first side and said first sides concave and/or said second side is convex so that said fluid flow tends to pivot the member away from the first side towards the second side, each said flap member also having a surface on the leading side of the pivot axis against which fluid flow reacts to oppose the tendency to pivot aforementioned.

5. An indicator as claimed in any one of claims 1, 2 and 4 wherein a said flap member has its first side facing in the same direction as the second side of an adjacent one of said flap members.

6. An indicator as claimed in any one of Claims 1 to 5 wherein the or each said flap member is bifurcated at the pivot axis.

7. An indicator as claimed in any of Claims 1 to 6 wherein the or each said flap member is formed with spacing bosses at the pivot axis.

8. A fluid flow indicatorsubstantially as herein before described with reference to and as illustrated in Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.