WO1989002065A1

WO1989002065A1 - Flow detector

Info

Publication number: WO1989002065A1
Application number: PCT/GB1988/000698
Authority: WO
Inventors: Adrian Scott
Original assignee: CHANGESTART Ltd
Current assignee: CHANGESTART Ltd
Priority date: 1987-08-28
Filing date: 1988-08-25
Publication date: 1989-03-09
Anticipated expiration: 1990-02-28
Also published as: AU2305288A; GB8720412D0

Abstract

The invention relates to flow detectors capable of detecting relatively small flow rates. The detector generally comprises a flow chamber (12) with an elongate closure element (17) of substantially uniform cross-section pivotally supported in said chamber (12). The pivotal axis for the element (17) is above the center of gravity for the element (17). In a no-flow condition element (17) hangs substantially vertical to close the end of a fluid inlet (18). The flow chamber (12) has such configuration that for the greater part of the displacement of the closure element (17) from a no-flow condition to a full flow condition the flow passage from the inlet (18) to an outlet (22) is around the element (17) and said flow passage has a substantially constant cross-section. In a preferred embodiment an array of sensors (23a to 23d) senses the position of the closure member (17) within the chamber.

Description

Flow detector

This invention relates to flow detectors and, more particularly, to a flow detector capable of sensing relatively small flow rates. Flow detectors are well known in the art and conventionally comprise a closure member, located in a fluid flow passage and displaceable between a "no- flow" position and a "flow" position or positions.

In most conventional flow detectors the closure member, in a no-flow condition, closes an aperture through which the supply fluid must flow to the flow passage and in a "flow" condition the closure member is displaced from its aperture closure position by the pressure of the supply fluid. Such prior art arrangements suffer from the disadvantages that the areas of the closure member acted upon by the supply fluid differ substantially for different positions of the closure member and the cross-sectional area of the flow passage past the closure member also varies considerably as the closure member is displaced from its no-flow position. These inherent disadvantages render such prior art devices relatively insensitive to small flow rates and can lead to "bounce" of the closure member.

The present invention seeks to provide a flow detector which is sensitive to relatively small flow rates.

According to the present invention there is provided a flow detector comprising a flow chamber, a closure member supported within said chamber and displaceable between a no-flow position and a flow position or positions, a fluid inlet to the chamber to one side of the closure member and a fluid outlet from said chamber on the other side of said closure member, characterised in that -the closure member is pivotably displaceable within said chamber from its no-flow position to its flow position or positions by fluid flow through the chamber.

Preferably the chamber is defined by two substantially parallel plane walls connected by a substantially continuous wall.

Preferably the closure member comprises an elongate element of substantially uniform cross section pivotably supported on a pivot the axis of which- lies at right angles to the planes of the two parallel walls, and each end of the elongate element sweeps, or lies closely adjacent to, a section of the continuous wall, which has an arcuate configuration based on a radius centred on the pivotable axis. Thus, the fluid flow passage past the elongate element is substantially constant for all those positions of the elongate element where the ends of the elongate element are sweeping their respective arcuate wall sections.

In a preferred embodiment in accordance with the invention the elongate element adopts a substantially vertical position in a no-flow condition through the chamber and the pivotal axis for the elongate element passes through the elongate element above the centre of the gravity of the element so that gravity urges the elongate element towards its no-flow position.

In a preferred embodiment in accordance with the invention the elongate element comprises, includes or supports a permanent magnet and the apparatus includes a sensor, such as a reed switch so located relative to the elongate element in a no- flow position that the permanent magnet closes the sensor only whilst the elongate element is in its no-flow position. The sensor may conveniently be in an electrical circuit which is activated when the sensor is activated by sensing the magnetic field indicative of a no-flow condition through the chamber, and which circuit is broken when the sensor is de-activated, indicative of a flow condition through the chamber. In a further embodiment an array of sensors ( reed switches) may be positioned to be- operated successively as the elongate element with the magnet is displaced between the no-flow position for the elongate element and the full flow position for said element. Conveniently the said array of reed switches may control electrical circuits which can, thereby, identify the degree of displacement of the elongate member from its no-flow position.

The invention will now be described further by way of example with reference to the accompanying drawings in which the single figure shows a cross - i -

section on the longitudinal centre line of a flow detector arrangement in accordance with the invention.

In the illustrated example the flow detector comprises a body, generally indicated by reference numeral 11, of rectangular configuration made from a non-ferrous material. A flow chamber, generally indicated by reference numeral 12, is cut into one face of the block 11 and, in practise, the chamber ₀ 12 will be closed by a plate of non-ferrous material (not shown in the drawings) secured to the face of block 11 by screws (not shown in the drawings).

The flow chamber recess 12 is of uniform depth so that the "bottom" 13 of the chamber 12 lies substantially parallel to the internal surface of the non-ferrous chamber closure plate (not shown). Thus, the bottom 13 of the flow chamber and the internal surface of the chamber closure plate define parallel side walls for the chamber and the "depth" o wall 14 of ^• the flow chamber 12 defines a substantially continuous wall connecting the side walls of the chamber 12.

In the illustrated example the flow detector is intended to operate with an external face 15 of the block 11 lowermost and substantially horizontal and, hereinafter, the terms "upper" and "lower" will apply to the device as the device is arranged to operate with the surface 15 lowermost and substantially horizontal. o A pivot pin 16 is outstanding from the plane of the bottom 13 of the recess, the axis of the pivot 16 being at right angles to the plane of bottom 13, and thereby horizontal when the external face 15 is horizontal, and a closure member 17 is pivotally J5 supported on the pivot 16.

The closure 17 is of substantially uniform rectangular cross section and the pivot pin 16 passes through the closure member 17 at a location spaced above the mid-regions of the member 17 and spaced from the upper end 17_a of the member 17, so

^■ that the centre of gravity for the element 17 is below the pivot 16.

A fluid flow inlet to the chamber 12 comprises an externally threaded tubular element 18 which passes through a threaded bore in the continuous

^■ ) wall 14 so as to protrude into the flow chamber 12 and the radial face of element 18 defines a seat for the closure member 17 in a no-flow condition. Lock nuts 19 and 20 on the element 18 serve to lock the said element in a desired axial location and allows

^■ - the tubular element 18 to be axially adjusted with respect to the block 11. A fluid supply duct 21 supplies fluid to the tubular element 18.

The element 18 enters into the lower regions of the flow chamber 12 and, in practise, is axially

: ₃ adjusted so as to disp^'lace the closure member 17 slightly to the right (as viewed in the drawing) of the free hanging position for the closure member 17. Thus, the closure member 17 exerts a very slight closure pressure on the seat defined by the inner

.5 radial face of the tubular element 18 and the "opening" pressure can. be varied by axially adjusting the element 18, and thereby the closure angle for the member 17.

As will be seen from the drawings the 0 continuous wall 14 in that region of the flow chamber adjacent the upper end 17ja of the element 17 is radiussed, as at 14a_, the radius being based on a radius from the axis of the pivot pin 16, so that the space between the end 17^ of element 16 and the 5 radiussed wall 14a. is substantially constant for all positions of the closure member 17 within the flow chamber 12.

In like manner the continuous wall 14 includes a radiussed section 14b_, based on a radius from the axis of the pivot pin 16 and which radius is slightly greater than the distance between the axis of pivot 16 and the lower end 17b_ of closure member 17 and the radiussed side wall section 14b_ is substantially constant for all positions of said end 17b_ adjacent the radiussed wall 14b_. As the member 17 is of substantially uniform cross section the clearance between the sides of member 17 and the bottom 13 and the closure plate (not shown) will be uniform for all positions of the member 17 within the chamber 12. A fluid flow outlet, defined by a tubular element 22, is entered through the side wall 14 to open into the flow chamber 12 at a location adjacent to the end 17b_ of member 17 when said member 17 is in position of- maximum displacement away from the tubular element 18 and said element 22 enters through the continuous wall 14 at a radiussed section 14^ of said wall 14. The radiussed section 14c_ is based on a centre between the pivot pin 16 and the wall section 14c_. As will be seen from the drawing the end 17b_ of the element 17 lies adjacent to the radiussed wall section 14b_ for some 80 to 85% of the total angle of displacement of the element 17 from its closure position abutting tubular element 18 to its "full flow" position (shown in broken line in the drawing) where the end 17b_ is most remote from the tubular element 18.

The block 11 further includes a bore 11a, in that side wall penetrated by the tubular element 18, and a sesor, comprising a reed switch 23 is supported in the bore 11a by a rod 24 with a nut 25 on its upper regions, and by which the depth of the reed switch 23 can be adjusted within the bore 24. The electrical connections 26 and 27 for the reed switch 23 extends through an axial bore in the rod 24 and extends out of the rod 24, above nuts 25, for connection to an electrical circuit to be described hereinafter.

The closure member 17 may comprise a permanent magnet but in the illustrated embodiment said member

' ) is constructed from a non ferrous material and support a permanent magnet 28. The magnet 28 is so selected that when the closure member 17 is in engagement with the tubular element 18, constituting a no-flow condition, the reed switch 23 is closed

"• but the said reed switch opens when the closure member 17 is displaced away from the tubular element 18. Fine tuning of the switching for the reed switch 23 is carried out by adjusting the axial length of the rod 24 within bore lla_^.

: ) With the above arrangement the sensitivity of the flow detector is adjusted by varying the axial length of the tubular element 18 protruding into the

'flow chamber 12, the clockwise rotation of the closure member 17 is limited by its abuttment with c ^". the tubular element 18 and the closer the centre of gravity of the closure member 17 and the magnet 28 approaches the vertical plane passing through the axis of the pivot 16 the more sensitive the device will become.

; ■^' With the axial length of the tubular element 18 adjusted the position of the reed switch 23 in the bore ll_a is adjusted so that, with the closure member 17 abutting tubular element 18 the reed switch 23 is closed and the said reed switch opens

; when the closure member 17 is displaced anti¬ clockwise from engagement with the tubular element 18.

With the closure member 17 abutting the tubular element 18 the detector device is in a no-flow condition, the reed switch 23 is closed and the electrical circuit, completed by the reed switch 23, can actuate display means (not shown) to indicate that the device is in a no-flow condition.

With a supply of fluid to the tubular element 18 such that the pressure of said fluid acting on -. that area of closure member 17 exposed to the bore of element 18 causes closure member 17 to be displaced anti-clockwise, the angular displacement of closure member 17 causes reed switch 23 to open, thus opening the electrical circuit controlled ι thereby to give a visual indication of flow, and the fluid flow from tubular element 18 is initially into that volume of flow chamber 12 to the left (as viewed in the drawings) of the closure member 17.

As the flow through tubular element 18 increases the pressure^• on the left hand face of closure member increases and member 17 is further angularly displaced in the anti-clockwise direction.

It should now be noted that the fluid flow passage from the chamber 12 to the left of the member 17, as viewed in the drawings, to the chamber 12 to the right of the member 17 is wholly around the member 17 that is to say via the clearance between the member 17 and the chamber walls and this clearance is constant^" for all positions of the ⁵ member 17 whilst the end 17a_^ of member 17 lies adjacent to the arcuate wall section 14b_. It should further be noted that as the member 17 is angularly displaced away from the no-flow position the centre of gravity of the member 17 and the magnet 28 moves away from the vertical plane passing through the axis of the pivot 16, so that the gravitational force urging the member 17 towards its no-flow position increases and the pressure difference across the member 17 displacing the member 17 away from its no-flow position must increase accordingly.

5 Thus, by locating an arcuate array of reed switches 23ji, 23b_ and 23c_^, so that said switches can be closed successively by the magnet 28 as the member 17 displaces from its no-flow position, valuable information regarding the location of the

1- member 17 within the chamber 12 and the flow conditions existing within the chamber 12 can be obtained.

When the member 17 has been so angularly displaced from its no-flow position that the end 17ci

1 of member 17 passes beyond the radiussed wall section • 14b_ the gap between the end 17ja and the radiussed wall section 1 c_^ progressively increases until the element ^'17 reaches its "full flow"

'.position, detectable by the reed switch 23cl, and in

2. which position the member 17 offers no obstruction to the free flow of fluid from the inlet 18 to the outlet 22.

Claims

1. A flow detector comprising a flow chamber, a closure member supported within said chamber and displaceable between a no-flow position and a flow position or positions, a fluid inlet to the chamber to one side of the closure member and a fluid outlet from said chamber on the other side of said closure member, characterised in that the closure member is pivotably displaceable within said chamber from its

10 no-flow position to its flow position or positions by fluid flow through the chamber.

2. A flow detector according to Claim 1 characterised in that the chamber is defined by two substantially parallel plane walls connected by a

15 substantially continuous wall and, in a condition of - use for the detector, said substantially parallel plane walls lie in substantially vertical planes.

3. A flow detector according to Claim 1 or 2 'characterised in that the closure member comprises

20 an elongate element of substantially uniform cross section.

4. A flow detector according to Claim 1, 2 or 3 characterised in that said closure member is supported for pivotal displacement within said flow

- 5 chamber and the pivotal axis for the closure member is above the centre of gravity for said member.

5. A flow detector according to Claim 4 characterised in that each end of the elongate member remote from the pivotal axis of said member lies closely adjacent to a section of the flow t chamber which has an arcuate configuration, based on a radius the centre of which is coincident with the axis of displacement for the elongate member, for the greater part of the displacement of said elongate member from a no-flow position thereof to a full flow position thereof..

6. A flow detector according to any proceeding claim characterised in that said flow chamber is defined by two substantially plane parallel walls, intended to be substantially vertical when the flow

1;. detector is in its position for use, connected by a continuous wall, the said closure member comprises an elongate element of substantially uniform cross section pivotally supported in said chamber for pivotal displacement about an axis at right angles to the planes of said parallel side walls, said pivotal axis passes through said elongate member 'above the centre of gravity for said member when the detector is in a position for use and wherein the flow passage past the closure member is of

2; substantially uniform cross sectional area for the greater part of the displacement of the closure member from a no-flow condition to a full flow condition for the detector.

7. A flow detector according to any preceding claim characterised in that the fluid inlet defines a valve seat engaged by the closure member in a no- flow condition for the detector.

8. A flow detector according to claim 7 characterised in that the fluid inlet is axially adjustable relative to said chamber.

9. A flow detector according to any preceding claim characterised in that the detector includes a magnetic field sensor, the said closure member has a magnetic field associated therewith and said sensor is arranged to detect the magnetic field only when the closure member is in a closure condition and to transmit a signal indicative of a flow/no-flow condition for the detector .

10. A flow detector according to Claim 9 characterised in that a plurality of magnetic field sensors are spaced apart to detect different positions of. the magnetic field associated with the closure member between the no-flow detected position and the fully open position of the closure member

-and each, of said plurality of magnetic field sensors is adapted,on detecting the magnetic field, o transmit a signal indicative of the sensed position

^•'of the closure member.