GB2189648A - Flow responsive device - Google Patents

Abstract

A flow responsive device includes first and second parallel cylindrical bores 11 and 12 formed in a body 10 of non-magnetic material and interconnected by a slot 14 extending along a common wall 13. A closely fitting float 15 is axially displaceable in the first bore 11 from a rest position in response to fluid pressure at an inlet I. When the float 15 is displaced, fluid flows from the inlet I along the first bore 11 through the slot 14 to the second bore 12 and out through an outlet O. The float 15 may be fitted with a magnet 19 for closing a relay 18 in response to movement of the magnet 19 along the first bore 11 so as to switch on, for example, a water pump of a domestic shower system. A compression spring 22 may be located in the first bore 11 to bias the float 15 towards the rest position. The first bore 11 may be calibrated so that the position of the float 15 provides a measure of the flow rate. <IMAGE>

Description

SPECIFICATION Flow responsive device This invention relates to a flow responsive device and it relates particularly, though not exclusively, to a flow responsive switch.

GB 1,604,247 describes a known flow responsive switch intended primarily to control a pump of a domestic shower system. The switch comprises a body formed with a cylindrical bore which interconnects an inlet and an outlet and which contains a control member displaceable axially in the bore in response to water pressure at the inlet. The control member is fitted internally with a magnet which causes the contact members of an externally mounted reed switch to close when the control member is displaced.

In practice it is found that the control member presents an appreciable obstacle to flow and, in some operational conditions, can cause a substantial loss of pressure at the outlet. This can be inconvenient, especially if the switch is used in conjunction with a pump designed to operate at relatively high hydrostatic pressures.

Accordingly there is provided a flow responsive device comprising a first fluid flow passageway having an inlet, a second fluid flow passageway having an outlet, means interconnecting said passageways, and a pressure responsive member within said first fluid flow passageway, wherein said pressure responsive member is displaceable with respect to the first fluid flow passageway from a rest position in dependence on the pressure of fluid at the inlet, and cooperates with said interconnecting means to regulate a flow of fluid from the first to the second fluid flow passageway in accordance with the extent of said displacement.

The device may include biasing means within said first flow passageway to bias the pressure responsive member towards said rest position.

The flow responsive device may be in the form of a flow responsive switch wherein said pressure responsive member may include a magnet and wherein switching means, responsive to displacement of the magnet in the first fluid flow passageway, is provided.

It is found that the flow rate through a device in accordance with the present invention can be regulated by the member to obtain a sufficient pressure at the outlet; this can be especially beneficial in the case of a pressure responsive switch used in conjunction with a pump (of a shower system, for example) operating at relatively high hydrostatic pressures. The device may also permit a high sensitivity to be obtained at low flow rates. The biasing means may conveniently be a compression spring.

In one embodiment of the invention said first fluid flow passageway comprises a bore (preferably cylindrical) in a body member, said interconnecting means comprises a slot extending along a wall of the bore and said pressure responsive member comprises a float, displaceable axially in the bore. The float is normally cylindrical, particularly if the bore is cylindrical, but other float shapes are possible eg a float with two disc-shaped ends connected by a rcd of smaller diameter, giving the float an I-shaped cross-section. Said first and second fluid flow passageways may both comprise respective cylindrical bores in said body member, the bores being arranged in side-by-side relationship.

The extent of a displacement is related to flow rate through the device and, in an embodiment of the invention, the first fluid flow passageway may be graduated to translate the axial postion of said pressure responsive member in the bore into a measure of flow rate.

In order that the invention may be carried readily into effect two embodiments thereof are now described, by way of example only, by reference to the accompanying drawings which each show a longitudinal, cross-sectional view through a respective flow responsive switch in accordance with the invention.

The flow responsive switches shown in the drawings are intended, primarily to control operation of a booster pump coupled into the water supply line of a domestic shower system or similar appliance. It will be appreciated, however, that the switches could find utility in other, allied applications, to control an intermittent pond pump, for example.

Referring to Fig. 1 of the drawings, a first embodiment of the invention comprises a body member 10, made of a suitable plastics or other non-magnetic material, formed with a first cylindrical bore 11 which is closed at one end thereof and has an inlet I at the other end, and a second cylindrical bore 12 which is also closed at one end and has an outlet 0 at the other end.

The two bores 11,12, which are arranged in side-by-side relationship, share a common wall 13 and are interconnected by a slot 14 extending lengthwise of the wall.

The first bore 11 accommodates a closely fitting, cylindrical float 15 which is displaced axially in the bore, from the shown rest position, in response to fluid pressure at the inlet. The float 15 is retained in the bore 11 by a retainer (not shown) such as a plastics or non-corrodable metal bar adjacent the inlet I. In order to achieve a satisfactory valve response, particularly at low pressure heads (eg 18" of water, static head) and/or low flow rates, one important characteristic to be considered is the relative size of the bore and float. It has been found that the preferred ratio of bore to float area was 0.6 to 0.93, more preferably 0.86 to 0.92. Thus a suitable result may be obtained by a float with a diameter of 12.8 mm in a bore with a diameter of 13.8 mm.

When the float 15 is displaced, fluid received at the inlet bypasses the float and is allowed to pass to the outlet via that part of slot 14 on the inlet side of the float. It will be appreciated, therefore, that the float regulates the flow of fluid in accordance with the extent of an axial displacement, which in turn, is related to the pressure of fluid at the inlet. In this way the switch can accommodate a desired flow rate and maintain an acceptable pressure at the outlet. It should be noted that the width of the slot 14 should be significantly smaller than the overall diameter of the float 15. If this is not the case, the float 15 tends to be sucked into the slot causing blocking or restriction of the flow.

A housing 17 mounted detachably on the body member, externally of, and adjacent to, the first bore 11 contains a reed relay 18, and the float 15 is fitted with a small magnet 19. The contact terminals 20 of the relay are caused to close in response to movement of the magnet along the bore when the float is displaced from the rest position. It will be appreciated that the relative axial dimensions of the bore and float and/or the axial position of the relay on the body member may be chosen suitably to achieve the optimum response and to ensure that the contact terminals of the relay remain in the closed condition while at least a preset minimum flow persists.

When the flow responsive switch is used in a domestic shower system, the inlet I and the outlet 0 are connected into the water supply line to the shower head on the upstream side of the pump, and the contact terminals of the reed relay are connected electrically to a power supply circuit for the pump.

When the shower is turned on, the switch responds to a flow of water in the supply line-the contact terminals close and power is supplied to the pump. When the shower is turned off the flow ceases causing the contact terminals to open and cutting off the supply of power to the pump.

It has been found that a flow responsive switch in accordance with the present invention, presenting a reduced pressure loss at the outlet, is particularly beneficial in a system using a relatively powerful pump which operates at higher hydrostatic pressures. The inventor has also found that the flow rate is related quantitatively to the axial displacement of the float along the first bore 11. The relationship between flow rate and displacement will of course, depend upon such parameters as the width, length and shape of the slot and if, as in this example, the slot is of uniform width, the axial displacement of the float is directly proportional to flow rate.

The first bore may be suitably calibrated to translate the axial position of the float in the passageway into a measure of the flow rate. Such calibration may serve as an ancillary feature of a flow responsive switch. Alternatively, though, in accordance with another aspect of the present invention, the reed relay and magnet could be omitted, the body member and float being used solely as a flow meter.

Fig. 2 illustrates a second embodiment having all the above-mentioned components of Fig. 1.

For clarity corresponding components in Figs. 1 and 2 have been given the same reference numbers.

Referring to Fig. 2, the second embodiment also includes a compression spring 22 which is located in the first bore 11 to act on the end 24 of the float 15 and the end 23 of the bore 11.

This spring 22 biases the float 15 towards the shown rest position irrespective of the direction of the longitudinal axis of the bore 11. This enables the flow responsive switch to operate efficiently with the bore 11 extending vertically, horizontally or in any intermediate position.

The compression spring 22 can be constructed of any suitable material, such as for example, stainless steel or copper.

In this specification by "rest position" is meant the position of the pressure responsive member, ie the float 15 which completely closes the slot 14. If the device includes switching means, ie the relay 18, the "rest position" is the position of the pressure responsive member in which the switching means is in the "off" position.

One example of a suitable compression spring is of 12.8 mm diameter and commences to respond at a static pressure head of 18" of water. In a preferred embodiment the device, except for the float 15, is made of a material marketed as Noryl GFN3, and the bores 11 and 12 each have a slight taper.

One example of a device of the invention has the following parameters: (a) Total length of bore 11 =55 mm (b) Length of float 15 =32 mm (c) Weight of float 15 = 7 gms (d) Length of uncompressed spring 22 =22 mm (e) Length of compressed spring 22 = 5 mm (f) Rate of spring 22 =0.004 N/mm The invention is not restricted to a device having these parameters.

The float 15 should be made from a less dense material than the remainder of the device to increase the sensitivity of the device. Examples of suitable materials are: Material S.G.

Polypropylene 0.9 Nylon 1.1 Noryl 731 1.1

Claims (12)

1. A flow responsive device comprising a first fluid flow passageway having an inlet, a second fluid flow passageway having an outlet, means interconnecting said passageways, and a pressure responsive member within said first fluid flow passageway, wherein said pressure responsive member is displaceable with respect to the first fluid flow passageway from a rest position in dependence on the pressure of fluid at the inlet, and operates with said interconnecting means to regulate a flow of fluid from the first to the second fluid flow passageway in accordance with the extent of said displacement.

2. A device as claimed in claim 1 including biasing means within first passageway to bias the pressure responsive member towards said rest position.

3. A device as claimed in claim 1 or 2 in which the pressure responsive member includes a magnet; the device including switching means responsive to displacement of the magnet in the first fluid flow passageway.

4. A device as claimed in any preceding claim in which the interconnecting means comprises a slot extending along the wall of the first fluid flow passageway.

5. A device as claimed in any preceding claim in which the first and second fluid flow passageways are arranged in side-by-side relationship.

6. A device as claimed in any preceding claim in which the first fluid flow passageway is calibrated to translate the axial position of the pressure responsive member into a measure of the fluid flow rate.

7. A device as claimed in any preceding claim in which the ratio of the cross-sectional area of the first fluid flow passageway to that of the pressure responsive member is in the range from 0.6 to 0.93.

8. A device as claimed in any preceding claim in which the ratio of the cross-sectionai area of the first fluid flow passageway to that of the pressure responsive member is in the range from 0.86 to 0.92.

9. A device as claimed in claim 2 in which the biasing means is a compression spring.

10. A device as claimed in claim 9 in which the compression spring is made of stainiess steel or copper.

11. A device as claimed in claim 9 or 10 in which the compression spring commences to respond at a static pressure head of 18" of water.

12. A flow responsive device substantially as herein described and shown in the accompanying drawings.